Adobe AIR includes a SQL database engine with support for local SQL databases with many standard SQL features, using the open source SQLite database system. The runtime does not specify how or where database data is stored on the file system. Each database is stored completely within a single file. A developer can specify the location in the file system where the database file is stored, and a single AIR application can access one or many separate databases (i.e. separate database files).

This document outlines the SQL syntax and data type support for Adobe AIR local SQL databases. This document is not intended to serve as a comprehensive SQL reference. Rather, it describes specific details of the SQL dialect that Adobe AIR supports. The runtime supports most of the SQL-92 standard SQL dialect. Because there are numerous references, web sites, books, and training materials for learning SQL, this document is not intended to be a comprehensive SQL reference or tutorial. Instead, this document particularly focuses on the Apollo AIR-supported SQL syntax, and the differences between SQL-92 and the supported SQL dialect.

The following topics are covered:

• Supported SQL syntax
• Data type support
• Conventions used in this document

Supported SQL syntax

This section describes the SQL syntax supported by the Adobe AIR SQL database engine. These listings are divided into explanations of different statement and clause types, expressions, built-in functions, and operators. The following topics are covered:

• General SQL syntax
• Data manipulation statements (SELECT, INSERT, UPDATE, and DELETE)
• Data definition statements (CREATE, ALTER, and DROP statements for tables, indices, views, and triggers)
• Special statements and clauses
• Built-in functions (Aggregate, scalar, and date/time formatting functions)
• Operators
• Parameters
• Unsupported SQL features
• Additional SQL features

General SQL syntax

In addition to the specific syntax for various statements and expressions, the following are general rules of SQL syntax:

• Case sensitivity: SQL statements, including object names, are not case sensitive. Nevertheless, SQL statements are frequently written with SQL keywords written in uppercase, and this document uses that convention. While SQL syntax is not case sensitive, literal text values in SQL are case sensitive, and comparison and sorting operations can be case sensitive, as specified by the collation sequence defined for a column or operation. For more information see COLLATE.
• White space: A white-space character (such as space, tab, new line, and so forth) must be used to separate individual words in an SQL statement. However, white space is optional between words and symbols. The type and quantity of white-space characters in a SQL statement is not significant. You can use white space, such as indenting and line breaks, to format your SQL statements for easy readability, without affecting the meaning of the statement.

Data manipulation statements

Data manipulation statements are the most commonly used SQL statements. These statements are used to retrieve, add, modify, and remove data from database tables. The following data manipulation statements are supported:

• SELECT
• INSERT
• UPDATE
• DELETE

SELECT

The SELECT statement is used to query the database. The result of a SELECT is zero or more rows of data where each row has a fixed number of columns. The number of columns in the result is specified by the result column name or expression list between the SELECT and optional FROM keywords.

sql-statement ::= SELECT [ALL | DISTINCT] result [FROM table-list] [WHERE expr] [GROUP BY expr-list] [HAVING expr] [compound-op select-statement]* [ORDER BY sort-expr-list] [LIMIT integer [( OFFSET | , ) integer]] result ::= result-column [, result-column]* result-column ::= * | table-name . * | expr [[AS] string] table-list ::= table [ join-op table join-args ]* table ::= table-name [AS alias] | ( select ) [AS alias] join-op ::= , | [NATURAL] [LEFT | RIGHT | FULL] [OUTER | INNER | CROSS] JOIN join-args ::= [ON expr] [USING ( id-list )] compound-op ::= UNION | UNION ALL | INTERSECT | EXCEPT sort-expr-list ::= expr [sort-order] [, expr [sort-order]]* sort-order ::= [COLLATE collation-name] [ASC | DESC] collation-name ::= BINARY | NOCASE

Any arbitrary expression can be used as a result. If a result expression is * then all columns of all tables are substituted for that one expression. If the expression is the name of a table followed by .* then the result is all columns in that one table.

The DISTINCT keyword causes a subset of result rows to be returned, in which each result row is different. NULL values are not treated as distinct from each other. The default behavior is that all result rows are returned, which can be made explicit with the keyword ALL.

The query is executed against one or more tables specified after the FROM keyword. If multiple table names are separated by commas, then the query uses the cross join of the various tables. The JOIN syntax can also be used to specify how tables are joined. The only type of outer join that is supported is LEFT OUTER JOIN. The ON clause expression in join-args must resolve to a boolean value. A subquery in parentheses may be used as a table in the FROM clause. The entire FROM clause may be omitted, in which case the result is a single row consisting of the values of the result expression list.

The WHERE clause is used to limit the number of rows the query retrieves. WHERE clause expressions must resolve to a boolean value. WHERE clause filtering is performed before any grouping, so WHERE clause expressions may not include aggregate functions.

The GROUP BY clause causes one or more rows of the result to be combined into a single row of output. A GROUP BY clause is especially useful when the result contains aggregate functions. The expressions in the GROUP BY clause do not have to be expressions that appear in the SELECT expression list.

The HAVING clause is like WHERE in that it limits the rows returned by the statement. However, the HAVING clause applies after any grouping specified by a GROUP BY clause has occurred. Consequently, the HAVING expression may refer to values that include aggregate functions. A HAVING clause expression is not required to appear in the SELECT list. Like a WHERE expression, a HAVING expression must resolve to a boolean value.

The ORDER BY clause causes the output rows to be sorted. The sort-expr-list argument to the ORDER BY clause is a list of expressions that are used as the key for the sort. The expressions do not have to be part of the result for a simple SELECT, but in a compound SELECT (a SELECT using one of the compound-op operators) each sort expression must exactly match one of the result columns. Each sort expression may be optionally followed by a sort-order clause consisting of the COLLATE keyword and the name of a collation function used for ordering text and/or the keyword ASC or DESC to specify the sort order (ascending or descending). The sort-order can be omitted and the default (ascending order) is used. For a definition of the COLLATE clause and collation functions, see COLLATE.

The LIMIT clause places an upper bound on the number of rows returned in the result. A negative LIMIT indicates no upper bound. The optional OFFSET following LIMIT specifies how many rows to skip at the beginning of the result set. In a compound SELECT query, the LIMIT clause may only appear after the final SELECT statement, and the limit is applied to the entire query. Note that if the OFFSET keyword is used in the LIMIT clause, then the limit is the first integer and the offset is the second integer. If a comma is used instead of the OFFSET keyword, then the offset is the first number and the limit is the second number. This seeming contradiction is intentional — it maximizes compatibility with legacy SQL database systems.

A compound SELECT is formed from two or more simple SELECT statements connected by one of the operators UNION, UNION ALL, INTERSECT, or EXCEPT. In a compound SELECT, all the constituent SELECT statements must specify the same number of result columns. There can only be a single ORDER BY clause after the final SELECT statement (and before the single LIMIT clause, if one is specified). The UNION and UNION ALL operators combine the results of the preceding and following SELECT statements into a single table. The difference is that in UNION, all result rows are distinct, but in UNION ALL, there may be duplicates. The INTERSECT operator takes the intersection of the results of the preceding and following SELECT statements. EXCEPT takes the result of preceding SELECT after removing the results of the following SELECT. When three or more SELECT statements are connected into a compound, they group from first to last.

For a definition of permitted expressions, see Expressions

INSERT

The INSERT statement comes in two basic forms and is used to populate tables with data.

sql-statement ::= INSERT [OR conflict-algorithm] INTO [database-name.] table-name [(column-list)] VALUES (value-list) | INSERT [OR conflict-algorithm] INTO [database-name.] table-name [(column-list)] select-statement REPLACE INTO [database-name.] table-name [(column-list)] VALUES (value-list) | REPLACE INTO [database-name.] table-name [(column-list)] select-statement

The first form (with the VALUES keyword) creates a single new row in an existing table. If no column-list is specified then the number of values must be the same as the number of columns in the table. If a column-list is specified, then the number of values must match the number of specified columns. Columns of the table that do not appear in the column list are filled with the default value defined when the table is created, or with NULL if no default value is defined.

The second form of the INSERT statement takes its data from a SELECT statement. The number of columns in the result of the SELECT must exactly match the number of columns in the table if column-list is not specified, or it must match the number of columns named in the column-list. A new entry is made in the table for every row of the SELECT result. The SELECT may be simple or compound. For a definition of allowable SELECT statements, see SELECT.

The optional conflict-algorithm allows the specification of an alternative constraint conflict resolution algorithm to use during this one command. For an explanation and definition of conflict algorithms, see ON CONFLICT (conflict algorithms).

The two REPLACE INTO forms of the statement are equivalent to using the standard INSERT [OR conflict-algorithm] form with the REPLACE conflict algorithm (i.e. the INSERT OR REPLACE... form).

UPDATE

The UPDATE statement is used to change the value of columns in a set of rows in a table.

sql-statement ::= UPDATE [OR conflict-algorithm] [database-name.] table-name SET assignment [, assignment]* [WHERE expr] conflict-algorithm ::= ROLLBACK | ABORT | FAIL | IGNORE | REPLACE assignment ::= column-name = expr

Each assignment in an UPDATE specifies a column name to the left of the equals sign and an arbitrary expression to the right. The expression may use the values of other columns. All expressions are evaluated before any assignments are made. For a definition of permitted expressions see Expressions.

The WHERE clause is used to restrict the rows that are updated. The WHERE clause expression must resolve to a boolean value.

The optional conflict-algorithm allows the specification of an alternative constraint conflict resolution algorithm to use during this one command. For an explanation and definition of conflict algorithms, see ON CONFLICT (conflict algorithms).

DELETE

The delete command is used to remove records from a table.

sql-statement ::= DELETE FROM [database-name.] table-name [WHERE expr]

The command consists of the DELETE FROM keywords followed by the name of the table from which records are to be removed.

Without a WHERE clause, all rows of the table are removed. If a WHERE clause is supplied, then only those rows that match the expression are removed. The WHERE clause expression must resolve to a boolean value. For a definition of permitted expressions, see Expressions.

Data definition statements

Data definition statements are used to create, modify, and remove database objects such as tables, views, indices, and triggers. The following data definition statements are supported:

• Tables:
  • CREATE TABLE
  • ALTER TABLE
  • DROP TABLE
• Indices:
  • CREATE INDEX
  • DROP INDEX
• Views:
  • CREATE VIEW
  • DROP VIEW
• Triggers:
  • CREATE TRIGGER
  • DROP TRIGGER

CREATE TABLE

A CREATE TABLE statement consists of the keywords CREATE TABLE followed by the name of the new table, then (in parentheses) a list of column definitions and constraints. The table name can be either an identifier or a string.

sql-statement ::= CREATE [TEMP | TEMPORARY] TABLE [IF NOT EXISTS] [database-name.] table-name ( column-def [, column-def]* [, constraint]* ) sql-statement ::= CREATE [TEMP | TEMPORARY] TABLE [database-name.] table-name AS select-statement column-def ::= name [type] [[CONSTRAINT name] column-constraint]* type ::= typename | typename ( number ) | typename ( number , number ) column-constraint ::= NOT NULL [ conflict-clause ] | PRIMARY KEY [sort-order] [ conflict-clause ] [AUTOINCREMENT] | UNIQUE [conflict-clause] | CHECK ( expr ) | DEFAULT default-value | COLLATE collation-name constraint ::= PRIMARY KEY ( column-list ) [conflict-clause] | UNIQUE ( column-list ) [conflict-clause] | CHECK ( expr ) conflict-clause ::= ON CONFLICT conflict-algorithm conflict-algorithm ::= ROLLBACK | ABORT | FAIL | IGNORE | REPLACE default-value ::= NULL | string | number | CURRENT_TIME | CURRENT_DATE | CURRENT_TIMESTAMP sort-order ::= ASC | DESC collation-name ::= BINARY | NOCASE column-list ::= column-name [, column-name]*

Each column definition is the name of the column followed by the data type for that column, then one or more optional column constraints. The data type for the column restricts what data may be stored in that column. If an attempt is made to store a value in a column with a different data type, the runtime converts the value to the appropriate type if possible, or raises an error. See the Data type support section for additional information.

The NOT NULL column constraint indicates that the column cannot contain NULL values.

A UNIQUE constraint causes an index to be created on the specified column or columns. This index must contain unique keys—no two rows may contain duplicate values or combinations of values for the specified column or columns. A CREATE TABLE statement can have multiple UNIQUE constraints, including multiple columns with a UNIQUE constraint in the column's definition and/or multiple table-level UNIQUE constraints.

A CHECK constraint defines an expression that is evaluated and must be true in order for a row's data to be inserted or updated. The CHECK expression must resolve to a boolean value.

A COLLATE clause in a column definition specifies what text collation function to use when comparing text entries for the column. The BINARY collating function is used by default. For details on the COLLATE clause and collation functions, see COLLATE.

The DEFAULT constraint specifies a default value to use when doing an INSERT. The value may be NULL, a string constant, or a number. The default value may also be one of the special case-independent keywords CURRENT_TIME, CURRENT_DATE or CURRENT_TIMESTAMP. If the value is NULL, a string constant, or a number, it is literally inserted into the column whenever an INSERT statement does not specify a value for the column. If the value is CURRENT_TIME, CURRENT_DATE or CURRENT_TIMESTAMP, then the current UTC date and/or time is inserted into the column. For CURRENT_TIME, the format is HH:MM:SS. For CURRENT_DATE, the format is YYYY-MM-DD. The format for CURRENT_TIMESTAMP is YYYY-MM-DD HH:MM:SS.

Specifying a PRIMARY KEY normally just creates a UNIQUE index on the corresponding column or columns. However, if the PRIMARY KEY constraint is on a single column that has the data type INTEGER (or one of its synonyms such as int) then that column is used by the database as the actual primary key for the table. This means that the column may only hold unique integer values. (Note that in many SQLite implementations, only the column type INTEGER causes the column to serve as the internal primary key, but in Adobe AIR synonyms for INTEGER such as int also specify that behavior.)

If a table does not have an INTEGER PRIMARY KEY column, an integer key is automatically generated when a row is inserted. The primary key for a row can always be accessed using one of the special names ROWID, OID, or _ROWID_. These names can be used regardless of whether it is an explicitly declared INTEGER PRIMARY KEY or an internal generated value. However, if the table has an explicit INTEGER PRIMARY KEY, the name of the column in the result data is the actual column name rather than the special name.

An INTEGER PRIMARY KEY column can also include the keyword AUTOINCREMENT. When the AUTOINCREMENT keyword is used, the database automatically generates and inserts a sequentially incremented integer key in the INTEGER PRIMARY KEY column when it executes an INSERT statement that doesn't specify an explicit value for the column.

There can only be one PRIMARY KEY constraint in a CREATE TABLE statement. It can either be part of one column's definition or one single table-level PRIMARY KEY constraint. A primary key column is implicitly NOT NULL.

The optional conflict-clause following many constraints allows the specification of an alternative default constraint conflict resolution algorithm for that constraint. The default is ABORT. Different constraints within the same table may have different default conflict resolution algorithms. If an INSERT or UPDATE statement specifies a different conflict resolution algorithm, that algorithm is used in place of the algorithm specified in the CREATE TABLE statement. See the section ON CONFLICT (conflict algorithms) for additional information.

Additional constraints, such as FOREIGN KEY constraints, do not result in an error but the runtime ignores them.

If the TEMP or TEMPORARY keyword occurs between CREATE and TABLE then the table that is created is only visible within the same database connection (SQLConnection instance). It is automatically deleted when the database connection is closed. Any indices created on a temporary table are also temporary. Temporary tables and indices are stored in a separate file distinct from the main database file.

If the optional database-name prefix is specified, then the table is created in a named database (a database that was connected to the SQLConnection instance by calling the attach() method with the specified database name). It is an error to specify both a database-name prefix and the TEMP keyword, unless the database-name prefix is temp. If no database name is specified, and the TEMP keyword is not present, the table is created in the main database (the database that was connected to the SQLConnection instance using the open() or openAsync()method).

There are no arbitrary limits on the number of columns or on the number of constraints in a table. There is also no arbitrary limit on the amount of data in a row.

The CREATE TABLE AS form defines the table as the result set of a query. The names of the table columns are the names of the columns in the result.

If the optional IF NOT EXISTS clause is present and another table with the same name already exists, then the database ignores the CREATE TABLE command.

A table can be removed using the DROP TABLE statement, and limited changes can be made using the ALTER TABLE statement.

ALTER TABLE

The ALTER TABLE command allows the user to rename or add a new column to an existing table. It is not possible to remove a column from a table.

sql-statement ::= ALTER TABLE [database-name.] table-name alteration alteration ::= RENAME TO new-table-name alteration ::= ADD [COLUMN] column-def

The RENAME TO syntax is used to rename the table identified by [database-name.] table-name to new-table-name. This command cannot be used to move a table between attached databases, only to rename a table within the same database.

If the table being renamed has triggers or indices, then they remain attached to the table after it has been renamed. However, if there are any view definitions or statements executed by triggers that refer to the table being renamed, they are not automatically modified to use the new table name. If a renamed table has associated views or triggers, you must manually drop and recreate the triggers or view definitions using the new table name.

The ADD [COLUMN] syntax is used to add a new column to an existing table. The new column is always appended to the end of the list of existing columns. The column-def clause may take any of the forms permissible in a CREATE TABLE statement, with the following restrictions:

• The column may not have a PRIMARY KEY or UNIQUE constraint.
• The column may not have a default value of CURRENT_TIME, CURRENT_DATE or CURRENT_TIMESTAMP.
• If a NOT NULL constraint is specified, the column must have a default value other than NULL.

The execution time of the ALTER TABLE statement is not affected by the amount of data in the table.

DROP TABLE

The DROP TABLE statement removes a table added with a CREATE TABLE statement. The table with the specified table-name is the table that's dropped. It is completely removed from the database and the disk file. The table cannot be recovered. All indices associated with the table are also deleted.

sql-statement ::= DROP TABLE [IF EXISTS] [database-name.] table-name

By default the DROP TABLE statement does not reduce the size of the database file. Empty space in the database is retained and used in subsequent INSERT operations. To remove free space in the database use the SQLConnection.clean() method. If the autoClean parameter is set to true when the database is initially created, the space is freed automatically.

The optional IF EXISTS clause suppresses the error that would normally result if the table does not exist.

CREATE INDEX

The CREATE INDEX command consists of the keywords CREATE INDEX followed by the name of the new index, the keyword ON, the name of a previously created table that is to be indexed, and a parenthesized list of names of columns in the table whose values are used for the index key.

sql-statement ::= CREATE [UNIQUE] INDEX [IF NOT EXISTS] [database-name.] index-name ON table-name ( column-name [, column-name]* ) column-name ::= name [COLLATE collation-name] [ASC | DESC]

Each column name can be followed by ASC or DESC keywords to indicate sort order, but the sort order designation is ignored by the runtime. Sorting is always done in ascending order.

The COLLATE clause following each column name defines a collating sequence used for text values in that column. The default collation sequence is the collation sequence defined for that column in the CREATE TABLE statement. If no collation sequence is specified, the BINARY collation sequence is used. For a definition of the COLLATE clause and collation functions see COLLATE.

There are no arbitrary limits on the number of indices that can be attached to a single table. There are also no limits on the number of columns in an index.

DROP INDEX

The drop index statement removes an index added with the CREATE INDEX statement. The specified index is completely removed from the database file. The only way to recover the index is to reenter the appropriate CREATE INDEX command.

sql-statement ::= DROP INDEX [IF EXISTS] [database-name.] index-name

By default the DROP INDEX statement does not reduce the size of the database file. Empty space in the database is retained and used in subsequent INSERT operations. To remove free space in the database use the SQLConnection.clean() method. If the autoClean parameter is set to true when the database is initially created, the space is freed automatically.

CREATE VIEW

The CREATE VIEW command assigns a name to a pre-defined SELECT statement. This new name can then be used in a FROM clause of another SELECT statement in place of a table name. Views are commonly used to simplify queries by combining a complex (and frequently used) set of data into a structure that can be used in other operations.

sql-statement ::= CREATE [TEMP | TEMPORARY] VIEW [IF NOT EXISTS] [database-name.] view-name AS select-statement

If the TEMP or TEMPORARY keyword occurs in between CREATE and VIEW then the view that is created is only visible to the SQLConnection instance that opened the database and is automatically deleted when the database is closed.

If a [database-name] is specified the view is created in the named database (a database that was connected to the SQLConnection instance using the attach() method, with the specified name argument. It is an error to specify both a [database-name] and the TEMP keyword unless the [database-name] is temp. If no database name is specified, and the TEMP keyword is not present, the view is created in the main database (the database that was connected to the SQLConnection instance using the open() or openAsync() method).

Views are read only. A DELETE, INSERT, or UPDATE statement cannot be used on a view, unless at least one trigger of the associated type (INSTEAD OF DELETE, INSTEAD OF INSERT, INSTEAD OF UPDATE) is defined. For information on creating a trigger for a view, see CREATE TRIGGER.

A view is removed from a database using the DROP VIEW statement.

DROP VIEW

The DROP VIEW statement removes a view created by a CREATE VIEW statement.

sql-statement ::= DROP VIEW [IF EXISTS] view-name

The specified view-name is the name of the view to drop. It is removed from the database, but no data in the underlying tables is modified.

CREATE TRIGGER

The create trigger statement is used to add triggers to the database schema. A trigger is a database operation (the trigger-action) that is automatically performed when a specified database event (the database-event) occurs.

sql-statement ::= CREATE [TEMP | TEMPORARY] TRIGGER [IF NOT EXISTS] [database-name.] trigger-name [BEFORE | AFTER] database-event ON table-name trigger-action sql-statement ::= CREATE [TEMP | TEMPORARY] TRIGGER [IF NOT EXISTS] [database-name.] trigger-name INSTEAD OF database-event ON view-name trigger-action database-event ::= DELETE | INSERT | UPDATE | UPDATE OF column-list trigger-action ::= [FOR EACH ROW] [WHEN expr] BEGIN trigger-step ; [ trigger-step ; ]* END trigger-step ::= update-statement | insert-statement | delete-statement | select-statement column-list ::= column-name [, column-name]*

A trigger is specified to fire whenever a DELETE, INSERT, or UPDATE of a particular database table occurs, or whenever an UPDATE of one or more specified columns of a table are updated. Triggers are permanent unless the TEMP or TEMPORARY keyword is used. In that case the trigger is removed when the SQLConnection instance's main database connection is closed. If no timing is specified (BEFORE or AFTER) the trigger defaults to BEFORE.

Only FOR EACH ROW triggers are supported, so the FOR EACH ROW text is optional. With a FOR EACH ROW trigger, the trigger-step statements are executed for each database row being inserted, updated or deleted by the statement causing the trigger to fire, if the WHEN clause expression evaluates to true.

If a WHEN clause is supplied, the SQL statements specified as trigger-steps are only executed for rows for which the WHEN clause is true. If no WHEN clause is supplied, the SQL statements are executed for all rows.

Within the body of a trigger, (the trigger-action clause) the pre-change and post-change values of the affected table are available using the special table names OLD and NEW. The structure of the OLD and NEW tables matches the structure of the table on which the trigger is created. The OLD table contains any rows that are modified or deleted by the triggering statement, in their state before the triggering statement's operations. The NEW table contains any rows that are modified or created by the triggering statement, in their state after the triggering statement's operations. Both the WHEN clause and the trigger-step statements can access values from the row being inserted, deleted or updated using references of the form NEW.column-name and OLD.column-name, where column-name is the name of a column from the table with which the trigger is associated. The availability of the OLD and NEW table references depends on the type of database-event the trigger handles:

• INSERT – NEW references are valid
• UPDATE – NEW and OLD references are valid
• DELETE – OLD references are valid

The specified timing (BEFORE, AFTER, or INSTEAD OF) determines when the trigger-step statements are executed relative to the insertion, modification or removal of the associated row. An ON CONFLICT clause may be specified as part of an UPDATE or INSERT statement in a trigger-step. However, if an ON CONFLICT clause is specified as part of the statement causing the trigger to fire, then that conflict handling policy is used instead.

In addition to table triggers, an INSTEAD OF trigger can be created on a view. If one or more INSTEAD OF INSERT, INSTEAD OF DELETE, or INSTEAD OF UPDATE triggers are defined on a view, it is not considered an error to execute the associated type of statement (INSERT, DELETE, or UPDATE) on the view. In that case, executing an INSERT, DELETE or UPDATE on the view causes the associated triggers to fire. Because the trigger is an INSTEAD OF trigger, the tables underlying the view are not modified by the statement that causes the trigger to fire. However, the triggers can be used to perform modifying operations on the underlying tables.

There is an important issue to keep in mind when creating a trigger on a table with an INTEGER PRIMARY KEY column. If a BEFORE trigger modifies the INTEGER PRIMARY KEY column of a row that is to be updated by the statement that causes the trigger to fire, the update doesn't occur. A workaround is to create the table with a PRIMARY KEY column instead of an INTEGER PRIMARY KEY column.

A trigger can be removed using the DROP TRIGGER statement. When a table or view is dropped, all triggers associated with that table or view are automatically dropped as well.

RAISE() function

A special SQL function RAISE() can be used in a trigger-step statement of a trigger. This function has the following syntax:

raise-function ::= RAISE ( ABORT, error-message ) | RAISE ( FAIL, error-message ) | RAISE ( ROLLBACK, error-message ) | RAISE ( IGNORE )

When one of the first three forms is called during trigger execution, the specified ON CONFLICT processing action (ABORT, FAIL, or ROLLBACK) is performed and the current statement's execution ends. The ROLLBACK is considered a statement execution failure, so the SQLStatement instance whose execute() method was being carried out dispatches an error (SQLErrorEvent.ERROR) event. The SQLError object in the dispatched event object's error property has its details property set to the error-message specified in the RAISE() function.

When RAISE(IGNORE) is called, the remainder of the current trigger, the statement that caused the trigger to execute, and any subsequent triggers that would have been executed are abandoned. No database changes are rolled back. If the statement that caused the trigger to execute is itself part of a trigger, that trigger program resumes execution at the beginning of the next step. For more information about the conflict resolution algorithms, see the section ON CONFLICT (conflict algorithms).

DROP TRIGGER

The DROP TRIGGER statement removes a trigger created by the CREATE TRIGGER statement.

sql-statement ::= DROP TRIGGER [IF EXISTS] [database-name.] trigger-name

The trigger is deleted from the database. Note that triggers are automatically dropped when their associated table is dropped.

Special statements and clauses

This section describes several clauses that are extensions to SQL provided by the runtime, as well as two language elements that can be used in many statements, comments and expressions. The elements in this section are:

• COLLATE clause
• EXPLAIN clause
• ON CONFLICT clause and conflict algorithms
• REINDEX statement
• Comments
• Expressions

COLLATE

The COLLATE clause is used in SELECT, CREATE TABLE, and CREATE INDEX statements to specify the comparison algorithm that is used when comparing or sorting values.

sql-statement ::= COLLATE collation-name collation-name ::= BINARY | NOCASE

The default collation type for columns is BINARY. When BINARY collation is used with values of the TEXT storage class, binary collation is performed by comparing the bytes in memory that represent the value regardless of the text encoding.

The NOCASE collation sequence is only applied for values of the TEXT storage class. When used, the NOCASE collation performs a case-insensitive comparison.

No collation sequence is used for storage classes of type NULL, BLOB, INTEGER, or REAL.

To use a collation type other than BINARY with a column, a COLLATE clause must be specified as part of the column definition in the CREATE TABLE statement. Whenever two TEXT values are compared, a collation sequence is used to determine the results of the comparison according to the following rules:

• For binary comparison operators (=, <, >, <=, and >=), if either operand is a column, then the default collation type of the column determines the collation sequence that is used for the comparison. If both operands are columns, then the collation type for the left operand determines the collation sequence used. If neither operand is a column, then the BINARY collation sequence is used.
• The BETWEEN...AND operator is equivalent to using two expressions with the >= and <= operators. For example, the expression x BETWEEN y AND z is equivalent to x >= y AND x <= z. Consequently, the BETWEEN...AND operator follows the preceding rule to determine the collation sequence.
• The IN operator behaves like the = operator for the purposes of determining the collation sequence to use. For example, the collation sequence used for the expression x IN (y, z) is the default collation type of x if x is a column. Otherwise, BINARY collation is used.
• An ORDER BY clause that is part of a SELECT statement may be explicitly assigned a collation sequence to be used for the sort operation. In that case the explicit collation sequence is always used. Otherwise, if the expression sorted by an ORDER BY clause is a column, the default collation type of the column is used to determine sort order. If the expression is not a column, the BINARY collation sequence is used.

EXPLAIN

The EXPLAIN command modifier is a non-standard extension to SQL.

sql-statement ::= EXPLAIN sql-statement

If the EXPLAIN keyword appears before any other SQL statement, then instead of actually executing the command, the result reports the sequence of virtual machine instructions it would have used to execute the command, had the EXPLAIN keyword not been present. The EXPLAIN feature is an advanced feature and allows developers to change SQL statement text in an attempt to optimize performance or debug a statement that doesn't appear to be working properly.

ON CONFLICT (conflict algorithms)

The ON CONFLICT clause is not a separate SQL command. It is a non-standard clause that can appear in many other SQL commands.

conflict-clause ::= ON CONFLICT conflict-algorithm conflict-clause ::= OR conflict-algorithm conflict-algorithm ::= ROLLBACK | ABORT | FAIL | IGNORE | REPLACE

The first form of the ON CONFLICT clause, using the keywords ON CONFLICT, is used in a CREATE TABLE statement. For an INSERT or UPDATE statement, the second form is used, with ON CONFLICT replaced by OR to make the syntax seem more natural. For example, instead of INSERT ON CONFLICT IGNORE, the statement becomes INSERT OR IGNORE. Although the keywords are different, the meaning of the clause is the same in either form.

The ON CONFLICT clause specifies the algorithm that is used to resolve constraint conflicts. The five algorithms are ROLLBACK, ABORT, FAIL, IGNORE, and REPLACE. The default algorithm is ABORT. The following is an explanation of the five conflict algorithms:

• ROLLBACK - When a constraint violation occurs, an immediate ROLLBACK occurs, ending the current transaction. The command aborts and the SQLStatement instance dispatches an error event. If no transaction is active (other than the implied transaction that is created on every command) then this algorithm works the same as ABORT.
• ABORT - When a constraint violation occurs, the command backs out any prior changes it might have made and the SQLStatement instance dispatches an error event. No ROLLBACK is executed, so changes from prior commands within a transaction are preserved. ABORT is the default behavior.
• FAIL - When a constraint violation occurs, the command aborts and the SQLStatement dispatches an error event. However, any changes to the database that the statement made before encountering the constraint violation are preserved and are not backed out. For example, if an UPDATE statement encounters a constraint violation on the 100th row that it attempts to update, then the first 99 row changes are preserved but changes to rows 100 and beyond don't occur.
• IGNORE - When a constraint violation occurs, the one row that contains the constraint violation is not inserted or changed. Aside from this row being ignored, the command continues executing normally. Other rows before and after the row that contained the constraint violation continue to be inserted or updated normally. No error is returned.
• REPLACE - When a UNIQUE constraint violation occurs, the pre-existing rows that are causing the constraint violation are removed before inserting or updating the current row. Consequently, the insert or update always occurs, and the command continues executing normally. No error is returned. If a NOT NULL constraint violation occurs, the NULL value is replaced by the default value for that column. If the column has no default value, then the ABORT algorithm is used. If a CHECK constraint violation occurs then the IGNORE algorithm is used. When this conflict resolution strategy deletes rows in order to satisfy a constraint, it does not invoke delete triggers on those rows.

The algorithm specified in the OR clause of an INSERT or UPDATE statement overrides any algorithm specified in a CREATE TABLE statement. If no algorithm is specified in the CREATE TABLE statement or the executing INSERT or UPDATE statement, the ABORT algorithm is used.

REINDEX

The REINDEX command is used to delete and re-create one or more indices. This command is useful when the definition of a collation sequence has changed.

sql-statement ::= REINDEX collation-name sql-statement ::= REINDEX [database-name .] ( table-name | index-name )

In the first form, all indices in all attached databases that use the named collation sequence are recreated. In the second form, when a table-name is specified, all indices associated with the table are rebuilt. If an index-name is given, only the specified index is deleted and recreated.

Comments

Comments aren't SQL commands, but they can occur in SQL queries. They are treated as white space by the runtime. They can begin anywhere white space can be found, including inside expressions that span multiple lines.

comment ::= single-line-comment | block-comment single-line-comment ::= -- single-line block-comment ::= /* multiple-lines or block [*/]

A single-line comment is indicated by two dashes. A single line comment only extends to the end of the current line.

Block comments can span any number of lines, or be embedded within a single line. If there is no terminating delimiter, a block comment extends to the end of the input. This situation is not treated as an error. A new SQL statement can begin on a line after a block comment ends. Block comments can be embedded anywhere white space can occur, including inside expressions, and in the middle of other SQL statements. Block comments do not nest. Single-line comments inside a block comment are ignored.

Expressions

Expressions are subcommands within other SQL blocks. The following describes the valid syntax for an expression within a SQL statement:

expr ::= expr binary-op expr | expr [NOT] like-op expr [ESCAPE expr] | unary-op expr | ( expr ) | column-name | table-name.column-name | database-name.table-name.column-name | literal-value | parameter | function-name( expr-list | * ) | expr ISNULL | expr NOTNULL | expr [NOT] BETWEEN expr AND expr | expr [NOT] IN ( value-list ) | expr [NOT] IN ( select-statement ) | expr [NOT] IN [database-name.] table-name | [EXISTS] ( select-statement ) | CASE [expr] ( WHEN expr THEN expr )+ [ELSE expr] END | CAST ( expr AS type ) | expr COLLATE collation-name like-op ::= LIKE | GLOB binary-op ::= see Operators unary-op ::= see Operators parameter ::= :param-name | @param-name | ? value-list ::= literal-value [, literal-value]* literal-value ::= literal-string | literal-number | literal-boolean | literal-blob | literal-null literal-string ::= 'string value' literal-number ::= integer | number literal-boolean ::= true | false literal-blob ::= X'string of hexadecimal data' literal-null ::= NULL

An expression is any combination of values and operators that can be resolved to a single value. Expressions can be divided into two general types, according to whether they resolve to a boolean (true or false) value or whether they resolve to a non-boolean value.

In several common situations, including in a WHERE clause, a HAVING clause, the ON expression in a JOIN clause, and a CHECK expression, the expression must resolve to a boolean value. The following types of expressions meet this condition:

• ISNULL
• NOTNULL
• IN ()
• EXISTS ()
• LIKE
• GLOB
• Certain functions
• Certain operators (specifically comparison operators)

Literal values

A literal numeric value is written as an integer number or a floating point number. Scientific notation is supported. The . (period) character is always used as the decimal point.

A string literal is indicated by enclosing the string in single quotes '. To include a single quote within a string, put two single quotes in a row like this example: ''.

A boolean literal is indicated by the value true or false. Literal boolean values are used with the Boolean column data type.

A BLOB literal is a string literal containing hexadecimal data and proceeded by a single x or X character, such as X'53514697465'.

A literal value can also be the token NULL.

Column name

A column name can be any of the names defined in the CREATE TABLE statement or one of the following special identifiers: ROWID, OID, or _ROWID_. These special identifiers all describe the unique random integer key (the "row key") associated with every row of every table. The special identifiers only refer to the row key if the CREATE TABLE statement does not define a real column with the same name. Row keys behave as read-only columns. A row key can be used anywhere a regular column can be used, except that you cannot change the value of a row key in an UPDATE or INSERT statement. The SELECT * FROM table statement does not include the row key in its result set.

SELECT statement

A SELECT statement can appear in an expression as either the right-hand operand of the IN operator, as a scalar quantity (a single result value), or as the operand of an EXISTS operator. When used as a scalar quantity or the operand of an IN operator, the SELECT can only have a single column in its result. A compound SELECT statement (connected with keywords like UNION or EXCEPT) is allowed. With the EXISTS operator, the columns in the result set of the SELECT are ignored and the expression returns TRUE if one or more rows exist and FALSE if the result set is empty. If no terms in the SELECT expression refer to the value in the containing query, then the expression is evaluated once before any other processing and the result is reused as necessary. If the SELECT expression does contain variables from the outer query, known as a correlated subquery, then the SELECT is re-evaluated every time it is needed.

When a SELECT is the right operand of the IN operator, the IN operator returns TRUE if the result of the left operand is equal to any of the values in the SELECT statement's result set. The IN operator may be preceded by the NOT keyword to invert the sense of the test.

When a SELECT appears within an expression but is not the right operand of an IN operator, then the first row of the result of the SELECT becomes the value used in the expression. If the SELECT yields more than one result row, all rows after the first are ignored. If the SELECT yields no rows, then the value of the SELECT is NULL.

CAST expression

A CAST expression changes the data type of the value specified to the one given. The type specified can be any non-empty type name that is valid for the type in a column definition of a CREATE TABLE statement. See Data type support for details.

Additional expression elements

These sections describe additional SQL elements that can be used in expressions:

• Built-in functions
  • Aggregate functions
  • Scalar functions
  • Date and time formatting functions
• Operators
• Parameters

Built-in functions

The built-in functions fall into three main categories:

• Aggregate functions
• Scalar functions
• Date and time formatting functions

In addition to these functions, there is a special function RAISE() that is used to provide notification of an error in the execution of a trigger. This function can only be used within the body of a CREATE TRIGGER statement. For information on the RAISE() function, see CREATE TRIGGER > RAISE().

Like all keywords in SQL, function names are not case sensitive.

Aggregate functions

Aggregate functions perform operations on values from multiple rows. These functions are primarily used in SELECT statements in conjunction with the GROUP BY clause.

AVG(X)	Returns the average value of all non-NULL X within a group. String and BLOB values that do not look like numbers are interpreted as 0. The result of AVG() is always a floating point value even if all inputs are integers.
COUNT(X) COUNT(*)	The first form return a count of the number of times that X is not NULL in a group. The second form (with the * argument) returns the total number of rows in the group.
MAX(X)	Returns the maximum value of all values in the group. The usual sort order is used to determine the maximum.
MIN(X)	Returns the minimum non-NULL value of all values in the group. The usual sort order is used to determine the minimum. If all values in the group are NULL, NULL is returned.
SUM(X) TOTAL(X)	Returns the numeric sum of all non-NULL values in the group. If all of the values are NULL then SUM() returns NULL, and TOTAL() returns 0.0. The result of TOTAL() is always a floating point value. The result of SUM() is an integer value if all non-NULL inputs are integers. If any input to SUM() is not an integer and not NULL then SUM() returns a floating point value. This value might be an approximation to the true sum.

In any of the preceding aggregate functions that take a single argument, that argument can be preceded by the keyword DISTINCT. In that case, duplicate elements are filtered before being passed into the aggregate function. For example, the function call COUNT(DISTINCT x) returns the number of distinct values of column X instead of the total number of non-NULL values in column x.

Scalar functions

Scalar functions operate on values one row at a time. The following is a list of these functions:

ABS(X)	Returns the absolute value of argument X.
COALESCE(X, Y, ...)	Returns a copy of the first non-NULL argument. If all arguments are NULL then NULL is returned. There must be at least two arguments.
GLOB(X, Y)	This function is used to implement the X GLOB Y syntax.
IFNULL(X, Y)	Returns a copy of the first non-NULL argument. If both arguments are NULL then NULL is returned. This function behaves the same as COALESCE().
HEX(X)	The argument is interpreted as a value of the BLOB storage type. The result is a hexadecimal rendering of the content of that value.
LAST_INSERT_ROWID()	Returns the row identifier (generated primary key) of the last row inserted to the database through the current SQLConnection. This value is the same as the value returned by the SQLConnection.lastInsertRowID property.
LENGTH(X)	Returns the string length of X in characters.
LIKE(X, Y [, Z])	This function is used to implement the X LIKE Y [ESCAPE Z] syntax of SQL. If the optional ESCAPE clause is present, then the function is invoked with three arguments. Otherwise, it is invoked with two arguments only.
LOWER(X)	Returns a copy of string X with all characters converted to lower case.
LTRIM(X) LTRIM(X, Y)	Returns a string formed by removing spaces from the left side of X. If a Y argument is specified, the function removes any of the characters in Y from the left side of X.
MAX(X, Y, ...)	Returns the argument with the maximum value. Arguments may be strings in addition to numbers. The maximum value is determined by the defined sort order. Note that MAX() is a simple function when it has 2 or more arguments but is an aggregate function when it has a single argument.
MIN(X, Y, ...)	Returns the argument with the minimum value. Arguments may be strings in addition to numbers. The minimum value is determined by the defined sort order. Note that MIN() is a simple function when it has 2 or more arguments but is an aggregate function when it has a single argument.
NULLIF(X, Y)	Returns the first argument if the arguments are different, otherwise returns NULL.
QUOTE(X)	This routine returns a string which is the value of its argument suitable for inclusion into another SQL statement. Strings are surrounded by single-quotes with escapes on interior quotes as needed. BLOB storage classes are encoded as hexadecimal literals. The function is useful when writing triggers to implement undo/redo functionality.
RANDOM(*)	Returns a pseudo-random integer between -9223372036854775808 and 9223372036854775807. This random value is not crypto-strong.
RANDOMBLOB(N)	Returns an N-byte BLOB containing pseudo-random bytes. N should be a positive integer. This random value is not crypto-strong. If the value of N is negative a single byte is returned.
ROUND(X) ROUND(X, Y)	Rounds off the number X to Y digits to the right of the decimal point. If the Y argument is omitted, 0 is used.
RTRIM(X) RTRIM(X, Y)	Returns a string formed by removing spaces from the right side of X. If a Y argument is specified, the function removes any of the characters in Y from the right side of X.
SUBSTR(X, Y, Z)	Returns a substring of input string X that begins with the Y-th character and which is Z characters long. The left-most character of X is index position 1. If Y is negative the first character of the substring is found by counting from the right rather than the left.
TRIM(X) TRIM(X, Y)	Returns a string formed by removing spaces from the left and right sides of X. If a Y argument is specified, the function removes any of the characters in Y from the left and right sides of X.
TYPEOF(X)	Returns the type of the expression X. The possible return values are 'null', 'integer', 'real', 'text', and 'blob'. For more information on data types see Data type support.
UPPER(X)	Returns a copy of input string X converted to all upper-case letters.
ZEROBLOB(N)	Returns a BLOB containing N bytes of 0x00.

Date and time formatting functions

The date and time formatting functions are a group of scalar functions that are used to create formatted date and time data. Note that these functions operate on and return string and number values. These functions are not intended to be used with the DATE data type. If you use these functions on data in a column whose declared data type is DATE, they do not behave as expected.

DATE(T, ...)	The DATE() function returns a string containing the date in this format: YYYY-MM-DD. The first parameter (T) specifies a time string of the format found under Time formats. Any number of modifiers can be specified after the time string. The modifiers can be found under Modifiers.
TIME(T, ...)	The TIME() function returns a string containing the time as HH:MM:SS. The first parameter (T) specifies a time string of the format found under Time formats. Any number of modifiers can be specified after the time string. The modifiers can be found under Modifiers.
DATETIME(T, ...)	The DATETIME() function returns a string containing the date and time in YYYY-MM-DD HH:MM:SS format. The first parameter (T) specifies a time string of the format found under Time formats. Any number of modifiers can be specified after the time string. The modifiers can be found under Modifiers.
JULIANDAY(T, ...)	The JULIANDAY() function returns a number indicating the number of days since noon in Greenwich on November 24, 4714 B.C. and the provided date. The first parameter (T) specifies a time string of the format found under Time formats. Any number of modifiers can be specified after the time string. The modifiers can be found under Modifiers.
STRFTIME(F, T, ...)	The STRFTIME() routine returns the date formatted according to the format string specified as the first argument F. The format string supports the following substitutions: %d day of month %f fractional seconds SS.SSS %H hour 00-24 %j day of year 001-366 %J Julian day number %m month 01-12 %M minute 00-59 %s seconds since 1970-01-01 %S seconds 00-59 %w day of week 0-6 (sunday = 0) %W week of year 00-53 %Y year 0000-9999 %% % The second parameter (T) specifies a time string of the format found under Time formats. Any number of modifiers can be specified after the time string. The modifiers can be found under Modifiers.

Time formats

A time string can be in any of the following formats:

YYYY-MM-DD	2007-06-15
YYYY-MM-DD HH:MM	2007-06-15 07:30
YYYY-MM-DD HH:MM:SS	2007-06-15 07:30:59
YYYY-MM-DD HH:MM:SS.SSS	2007-06-15 07:30:59.152
YYYY-MM-DDTHH:MM	2007-06-15T07:30
YYYY-MM-DDTHH:MM:SS	2007-06-15T07:30:59
YYYY-MM-DDTHH:MM:SS.SSS	2007-06-15T07:30:59.152
HH:MM	07:30 (date is 2000-01-01)
HH:MM:SS	07:30:59 (date is 2000-01-01)
HH:MM:SS.SSS	07:30:59:152 (date is 2000-01-01)
now	Current date and time in Universal Coordinated Time.
DDDD.DDDD	Julian day number as a floating point number

The character T in these formats is a literal character "T" separating the date and the time. Formats that only include a time assume the date 2001-01-01.

Modifiers

The time string can be followed by zero or more modifiers that alter the date or alter the interpretation of the date. The available modifiers are as follows:

NNN days	Number of days to add to the time.
NNN hours	Number of hours to add to the time.
NNN minutes	Number of minutes to add to the time.
NNN.NNNN seconds	Number of seconds and milliseconds to add to the time.
NNN months	Number of months to add to the time.
NNN years	Number of years to add to the time.
start of month	Shift time backwards to the start of the month.
start of year	Shift time backwards to the start of the year.
start of day	Shift time backwards to the start of the day.
weekday N	Forwards the time to the specified weekday. (0 = Sunday, 1 = Monday, and so forth)
localtime	Converts the date to local time
utc	Converts the date to Universal Coordinated Time

Operators

SQL supports a large selection of operators, including common operators that exist in most programming languages, as well as several operators that are unique to SQL.

Common operators

The following binary operators are allowed in a SQL block and are listed in order from highest to lowest precedence:

|| * / % + - << >> & | < <= > >= = == != <> IN AND OR

Supported unary prefix operators are:

- ! ~ NOT

The COLLATE operator can be thought of as a unary postfix operator. The COLLATE operator has the highest precedence. It always binds more tightly than any prefix unary operator or any binary operator.

Note that there are two variations of the equals and not equals operators. Equals can be either = or ==. The not-equals operator can be either != or <>.

The || operator is the string concatenation operator—it joins together the two strings of its operands.

The operator % outputs the remainder of its left operand modulo its right operand.

The result of any binary operator is a numeric value, except for the || concatenation operator which gives a string result.

SQL operators

LIKE

The LIKE operator does a pattern matching comparison.

expr ::= (column-name | expr) LIKE pattern pattern ::= '[ string | % | _ ]'

The operand to the right of the LIKE operator contains the pattern, and the left-hand operand contains the string to match against the pattern. A percent symbol (%) in the pattern is a wildcard character—it matches any sequence of zero or more characters in the string. An underscore (_) in the pattern matches any single character in the string. Any other character matches itself or its lower/upper case equivalent, that is, matches are performed in a case-insensitive manner. (Note: the database engine only understands upper/lower case for 7-bit Latin characters. Consequently, the LIKE operator is case sensitive for 8-bit iso8859 characters or UTF-8 characters. For example, the expression 'a' LIKE 'A' is TRUE but 'æ' LIKE 'Æ' is FALSE). Case sensitivity for Latin characters can be changed using the SQLConnection.caseSensitiveLike property.

If the optional ESCAPE clause is present, then the expression following the ESCAPE keyword must evaluate to a string consisting of a single character. This character may be used in the LIKE pattern to match literal percent or underscore characters. The escape character followed by a percent symbol, underscore or itself matches a literal percent symbol, underscore or escape character in the string, respectively.

GLOB

The GLOB operator is similar to LIKE but uses the Unix file globbing syntax for its wildcards. Unlike LIKE, GLOB is case sensitive.

IN

The IN operator calculates whether its left operand is equal to one of the values in its right operand (a set of values in parentheses).

in-expr ::= expr [NOT] IN ( value-list ) | expr [NOT] IN ( select-statement ) | expr [NOT] IN [database-name.] table-name value-list ::= literal-value [, literal-value]*

The right operand can be a set of comma-separated literal values, or it can be the result of a SELECT statement. See SELECT statements in expressions for an explanation and limitations on using a SELECT statement as the right-hand operand of the IN operator.

BETWEEN...AND

The BETWEEN...AND operator is equivalent to using two expressions with the >= and <= operators. For example, the expression x BETWEEN y AND z is equivalent to x >= y AND x <= z.

NOT

The NOT operator is a negation operator. The GLOB, LIKE, and IN operators may be preceded by the NOT keyword to invert the sense of the test (in other words, to check that a value does not match the indicated pattern).

Parameters

A parameter specifies a placeholder in the expression for a literal value that is filled in at runtime by assigning a value to the SQLStatement.parameters associative array. Parameters can take three forms:

?	A question mark indicates an indexed parameter. Parameters are assigned numerical (zero-based) index values according to their order in the statement.
:AAAA	A colon followed by an identifier name holds a spot for a named parameter with the name AAAA. Named parameters are also numbered according to their order in the SQL statement. To avoid confusion, it is best to avoid mixing named and numbered parameters.
@AAAA	An "at sign" is equivalent to a colon.

Unsupported SQL features

The following is a list of the standard SQL elements that are not supported in Adobe AIR:

• FOREIGN KEY constraints - FOREIGN KEY constraints are parsed but are not enforced.
• Triggers - FOR EACH STATEMENT triggers are not supported (all triggers must be FOR EACH ROW). INSTEAD OF triggers are not supported on tables (INSTEAD OF triggers are only allowed on views). Recursive triggers—triggers that trigger themselves—are not supported.
• ALTER TABLE - Only the RENAME TABLE and ADD COLUMN variants of the ALTER TABLE command are supported. Other kinds of ALTER TABLE operations such as DROP COLUMN, ALTER COLUMN, ADD CONSTRAINT, and so forth are ignored.
• Nested transactions - Only a single active transaction is allowed.
• RIGHT and FULL OUTER JOIN - RIGHT OUTER JOIN or FULL OUTER JOIN are not supported.
• Updateable VIEW - A view is read only. You may not execute a DELETE, INSERT, or UPDATE statement on a view. An INSTEAD OF trigger that fires on an attempt to DELETE, INSERT, or UPDATE a view is supported and can be used to update supporting tables in the body of the trigger.
• GRANT and REVOKE- A database is an ordinary disk file; the only access permissions that can be applied are the normal file access permissions of the underlying operating system. The GRANT and REVOKE commands commonly found on client/server RDBMSes are not implemented.

The following SQL elements and SQLite features are supported in some SQLite implementations, but are not supported in Adobe AIR. Most of this functionality is available through methods of the SQLConnection class:

• Transaction-related SQL elements (BEGIN, END, COMMIT, ROLLBACK): This functionality is available through the transaction-related methods of the SQLConnection class: SQLConnection.begin(), SQLConnection.commit(), and SQLConnection.rollback().
• ANALYZE: This functionality is available through the SQLConnection.analyze() method.
• ATTACH: This functionality is available through the SQLConnection.attach() method.
• COPY: This statement is not supported.
• CREATE VIRTUAL TABLE: This statement is not supported.
• DETACH: This functionality is available through the SQLConnection.detach() method.
• PRAGMA: This statement is not supported.
• VACUUM: This functionality is available through the SQLConnection.compact() method.
• System table access is not available: The system tables including sqlite_master and other tables with the "sqlite_" prefix are not available in SQL statements. The runtime includes a schema API that provides an object-oriented way to access schema data. For more information see the SQLConnection.loadSchema() method.
• SQLITE_VERSION() function: The sqlite_version() function is not available for use in SQL statements.
• Regular-expression functions (MATCH() and REGEX()): These functions are not available in SQL statements.

The following functionality differs between many SQLite implementations and Adobe AIR:

• Indexed statement parameters: In many implementations indexed statement parameters are one-based. However, in Adobe AIR indexed statement parameters are zero-based (that is, the first parameter is given the index 0, the second parameter is given the index 1, and so forth.
• INTEGER PRIMARY KEY column definitions: In many implementations, only columns that are defined exactly as INTEGER PRIMARY KEY are used as the actual primary key column for a table. In those implementations, using another data type that is usually a synonym for INTEGER (such as int) does not cause the column to be used as the internal primary key. However, in Adobe AIR, the int data type (and other INTEGER synonyms) are considered exactly equivalent to INTEGER. Consequently, a column defined as int PRIMARY KEY is used as the internal primary key for a table. For more information, see the sections CREATE TABLE and Column affinity.

Additional SQL features

The following column affinity types are not supported by default in SQLite, but are supported in Adobe AIR (Note that, like all keywords in SQL, these data type names are not case-sensitive):

• Boolean: corresponding to the Boolean class.
• Date: corresponding to the Date class.
• int: corresponding to the int class (equivalent to the INTEGER column affinity).
• Number: corresponding to the Number class (equivalent to the REAL column affinity).
• Object: corresponding to the Object class or any subclass that can be serialized and deserialized using AMF3. (This includes most classes including custom classes, but excludes some classes including display objects and objects that include display objects as properties.)
• String: corresponding to the String class (equivalent to the TEXT column affinity).
• XML: corresponding to the ActionScript (E4X) XML class.
• XMLList: corresponding to the ActionScript (E4X) XMLList class.

The following literal values are not supported by default in SQLite, but are supported in Adobe AIR:

• true: used to represent the literal boolean value true, for working with BOOLEAN columns.
• false: used to represent the literal boolean value false, for working with BOOLEAN columns.

Data type support

Unlike most SQL databases, the Adobe AIR SQL database engine does not require or enforce that table columns contain values of a certain type. Instead, the runtime uses two concepts, storage classes and column affinity, to control data types. This section describes storage classes and column affinity, as well as how data type differences are resolved under various conditions:

• Storage classes
• Column affinity
• Data types and comparison operators
• Data types and mathematical operators
• Data types and sorting
• Data types and grouping
• Data types and compound SELECT statements

Storage classes

Storage classes represent the actual data types that are used to store values in a database. The following storage classes are used by the database:

• NULL - The value is a NULL value.
• INTEGER - The value is a signed integer.
• REAL - The value is a floating point number value.
• TEXT - The value is a text string (limited to 256 MB).
• BLOB - The value is a Binary Large Object (BLOB); in other words, raw binary data (limited to 256 MB).

All values supplied to the database as literals embedded in a SQL statement or values bound using parameters to a prepared SQL statement are assigned a storage class before the SQL statement is executed.

Literals that are part of a SQL statement are assigned storage class TEXT if they are enclosed by single or double quotes, INTEGER if the literal is specified as an unquoted number with no decimal point or exponent, REAL if the literal is an unquoted number with a decimal point or exponent and NULL if the value is a NULL. Literals with storage class BLOB are specified using the X'ABCD' notation. For more information, see Literal values in expressions.

Values supplied as parameters using the SQLStatement.parameters associative array are assigned the storage class that most closely matches the native data type bound. For example, int values are bound as INTEGER storage class, Number values are given the REAL storage class, String values are given the TEXT storage class, and ByteArray objects are given the BLOB storage class.

Column affinity

The affinity of a column is the recommended type for data stored in that column. When a value is stored in a column (through an INSERT or UPDATE statement), the runtime attempts to convert that value from its data type to the specified affinity. For example, if a Date value (an ActionScript or JavaScript Date instance) is inserted into a column whose affinity is TEXT, the Date value is converted to the String representation (equivalent to calling the object's toString() method) before being stored in the database. If the value cannot be converted to the specified affinity an error occurs and the operation is not performed. When a value is retrieved from the database using a SELECT statement, it is returned as an instance of the class corresponding to the affinity, regardless of whether it was converted from a different data type when it was stored.

If a column accepts NULL values, the ActionScript or JavaScript value null can be used as a parameter value to store NULL in the column. When a NULL storage class value is retrieved in a SELECT statement, it is always returned as the ActionScript or JavaScript value null, regardless of the column's affinity. If a column accepts NULL values, always check values retrieved from that column to determine if they're null before attempting to cast the values to a non-nullable type (such as Number or Boolean).

Each column in the database is assigned one of the following type affinities:

• TEXT (or String)
• NUMERIC
• INTEGER (or int)
• REAL (or Number)
• Boolean
• Date
• XML
• XMLList
• Object
• NONE

TEXT (or String)

A column with TEXT or String affinity stores all data using storage classes NULL, TEXT, or BLOB. If numerical data is inserted into a column with TEXT affinity it is converted to text form before being stored.

NUMERIC

A column with NUMERIC affinity contains values using storage classes NULL, REAL, or INTEGER. When text data is inserted into a NUMERIC column, an attempt is made to convert it to an integer or real number before it is stored. If the conversion is successful, then the value is stored using the INTEGER or REAL storage class (for example, a value of '10.05' is converted to REAL storage class before being stored). If the conversion cannot be performed an error occurs. No attempt is made to convert a NULL value. A value that's retrieved from a NUMERIC column is returned as an instance of the most specific numeric type into which the value fits. In other words, if the value is a positive integer or 0, it's returned as a uint instance. If it's a negative integer, it's returned as an int instance. Finally, if it has a floating point component (it's not an integer) it's returned as a Number instance.

INTEGER (or int)

A column that uses INTEGER affinity behaves in the same way as a column with NUMERIC affinity, with one exception. If the value to be stored is a real value (such as a Number instance) with no floating point component or if the value is a text value that can be converted to a real value with no floating point component, it is converted to an integer and stored using the INTEGER storage class. If an attempt is made to store a real value with a floating point component an error occurs.

REAL (or Number)

A column with REAL or NUMBER affinity behaves like a column with NUMERIC affinity except that it forces integer values into floating point representation. A value in a REAL column is always returned from the database as a Number instance.

Boolean

A column with Boolean affinity stores true or false values. A Boolean column accepts a value that is an ActionScript or JavaScript Boolean instance. If code attempts to store a String value, a String with a length greater than zero is considered true, and an empty String is false. If code attempts to store numeric data, any non-zero value is stored as true and 0 is stored as false. When a Boolean value is retrieved using a SELECT statement, it is returned as a Boolean instance. Non-NULL values are stored using the INTEGER storage class (0 for false and 1 for true) and are converted to Boolean objects when data is retrieved.

Date

A column with Date affinity stores date and time values. A Date column is designed to accept values that are ActionScript or JavaScript Date instances. If an attempt is made to store a String value in a Date column, the runtime attempts to convert it to a Julian date. If the conversion fails an error occurs. If code attempts to store a Number, int, or uint value, no attempt is made to validate the data and it is assumed to be a valid Julian date value. A Date value that's retrieved using a SELECT statement is automatically converted to a Date instance. Date values are stored as Julian date values using the REAL storage class, so sorting and comparing operations work as you would expect them to.

XML or XMLList

A column that uses XML or XMLList affinity stores XML structures. When code attempts to store data in an XML column using a SQLStatement parameter the runtime attempts to convert and validate the value using the ActionScript XML() or XMLList() function. If the value cannot be converted to valid XML an error occurs. If the attempt to store the data uses a literal SQL text value (for example INSERT INTO (col1) VALUES ('Invalid XML (no closing tag)'), the value is not parsed or validated — it is assumed to be well-formed. If an invalid value is stored, when it is retrieved it is returned as an empty XML object. XML and XMLList Data is stored using the TEXT storage class or the NULL storage class.

Object

A column with Object affinity stores ActionScript or JavaScript complex objects, including Object class instances as well as instances of Object subclasses such as Array instances and even custom class instances. Object column data is serialized in AMF3 format and stored using the BLOB storage class. When a value is retrieved, it is deserialized from AMF3 and returned as an instance of the class as it was stored. Note that some ActionScript classes, notably display objects, cannot be deserialized as instances of their original data type. Before storing a custom class instance, you must register an alias for the class using the flash.net.registerClassAlias() method (or in Flex by adding [RemoteObject] metadata to the class declaration). Also, before retrieving that data you must register the same alias for the class. Any data that can't be deserialized properly, either because the class inherently can't be deserialized or because of a missing or mismatched class alias, is returned as an anonymous object (an Object class instance) with properties and values corresponding to the original instance as stored.

NONE

A column with affinity NONE does not prefer one storage class over another. It makes no attempt to convert data before it is inserted.

Determining affinity

The type affinity of a column is determined by the declared type of the column in the CREATE TABLE statement. When determining the type the following rules (not case-sensitive) are applied:

• If the data type of the column contains any of the strings "CHAR", "CLOB", "STRI", or "TEXT" then that column has TEXT/String affinity. Notice that the type VARCHAR contains the string "CHAR" and is thus assigned TEXT affinity.
• If the data type for the column contains the string "BLOB" or if no data type is specified then the column has affinity NONE.
• If the data type for column contains the string "XMLL" then the column has XMLList affinity.
• If the data type is the string "XML" then the column has XML affinity.
• If the data type contains the string "OBJE" then the column has Object affinity.
• If the data type contains the string "BOOL" then the column has Boolean affinity.
• If the data type contains the string "DATE" then the column has Date affinity.
• If the data type contains the string "INT" (including "UINT") then it is assigned INTEGER/int affinity.
• If the data type for a column contains any of the strings "REAL", "NUMB", "FLOA", or "DOUB" then the column has REAL/Number affinity.
• Otherwise, the affinity is NUMERIC.
• If a table is created using a CREATE TABLE t AS SELECT... statement then all columns have no data type specified and they are given the affinity NONE.

Data types and comparison operators

The following binary comparison operators =, <, <=, >= and != are supported, along with an operation to test for set membership, IN, and the ternary comparison operator BETWEEN. For details about these operators see Operators.

The results of a comparison depend on the storage classes of the two values being compared. When comparing two values the following rules are applied:

• A value with storage class NULL is considered less than any other value (including another value with storage class NULL).
• An INTEGER or REAL value is less than any TEXT or BLOB value. When an INTEGER or REAL is compared to another INTEGER or REAL, a numerical comparison is performed.
• A TEXT value is less than a BLOB value. When two TEXT values are compared, a binary comparison is performed.
• When two BLOB values are compared, the result is always determined using a binary comparison.

When making binary comparisons between numeric and text storage classes, if necessary the database attempts to convert the values before performing the comparison. When comparing number and text storage classes the following rules are applied (Note: the term expression used in the following rules includes any SQL scalar expression or literal other than a column value. For example, if X and Y.Z are column names, then +X and +Y.Z are considered expressions):

• When a column value is compared to the result of an expression, the affinity of the column is applied to the result of the expression before the comparison takes place.
• When two column values are compared, if one column has INTEGER, REAL, or NUMERIC affinity and the other does not, then NUMERIC affinity is applied to any values with storage class TEXT extracted from the non-NUMERIC column.
• When the results of two expressions are compared, no conversions occur. The results are compared as-is. If a string is compared to a number, the number is always less than the string.

The ternary operator BETWEEN is always recast as the equivalent binary expression. For example, a BETWEEN b AND c is recast to a >= b AND a <= c, even if this means that different affinities are applied to a in each of the comparisons required to evaluate the expression.

Expressions of the type a IN (SELECT b ....) are handled by the three rules enumerated previously for binary comparisons, that is, in a similar manner to a = b. For example, if b is a column value and a is an expression, then the affinity of b is applied to a before any comparisons take place. The expression a IN (x, y, z) is recast as a = +x OR a = +y OR a = +z. The values to the right of the IN operator (the x, y, and z values in this example) are considered to be expressions, even if they happen to be column values. If the value of the left of the IN operator is a column, then the affinity of that column is used. If the value is an expression then no conversions occur.

How comparisons are performed can also be affected by the use of a COLLATE clause. For more information, see COLLATE.

Data types and mathematical operators

For each of the supported mathematical operators, *, /, %, +, and -, numeric affinity is applied to each operand before evaluating the expression. If any operand cannot be converted to the NUMERIC storage class successfully the expression evaluates to NULL.

When the concatenation operator || is used each operand is converted to the TEXT storage class before the expression is evaluated. If any operand cannot be converted to the TEXT storage class then the result of the expression is NULL. This inability to convert the value can happen in two situations, if the value of the operand is NULL, or if it's a BLOB containing a non-TEXT storage class.

Data types and sorting

When values are sorted by an ORDER BY clause, values with storage class NULL come first. These are followed by INTEGER and REAL values interspersed in numeric order, followed by TEXT values in binary order or based on the specified collation (BINARY or NOCASE). Finally come BLOB values in binary order. No storage class conversions occur before the sort.

Data types and grouping

When grouping values with the GROUP BY clause, values with different storage classes are considered distinct. An exception is INTEGER and REAL values which are considered equal if they are numerically equivalent. No affinities are applied to any values as the result of a GROUP BY clause.

Data types and compound SELECT statements

The compound SELECT operators UNION, INTERSECT, and EXCEPT perform implicit comparisons between values. Before these comparisons are performed an affinity may be applied to each value. The same affinity, if any, is applied to all values that may be returned in a single column of the compound SELECT result set. The affinity that is applied is the affinity of the column returned by the first component SELECT statement that has a column value (and not some other kind of expression) in that position. If for a given compound SELECT column none of the component SELECT statements return a column value, no affinity is applied to the values from that column before they are compared.

Conventions used in this document

Within statement definitions in this document, the following conventions are used:

• Text case
  • UPPER CASE - literal SQL keywords are written in all upper case
  • lower case - placeholder terms or clause names are written in all lower case
• Definition characters
  • ::= - indicates a clause or statement definition
• Grouping and alternating characters
  • | - the pipe character is used between alternative options, and can be read as "or"
  • [] - items in square brackets are optional items; the brackets can contain a single item or a set of alternative items
  • () - parentheses surrounding a set of alternatives (a set of items separated by pipe characters), designates a required group of items, that is, a set of items that are the possible values for a single required item
• Quantifiers
  • + - a plus character following an item in parentheses indicates that the preceding item can occur 1 or more times
  • * - an asterisk character following an item in square brackets indicates that the preceding (bracketed) item can occur 0 or more times
• Literal characters
  • * - an asterisk character used in a column name or between the parentheses following a function name signifies a literal asterisk character rather than the "0 or more" quantifier
  • . - a period character represents a literal period
  • , - a comma character represents a literal comma
  • () - a pair of parentheses surrounding a single clause or item indicates that the parentheses are required, literal parentheses characters.
  • Other characters - unless otherwise indicated, other characters represent those literal characters

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Fri Mar 19 2010, 03:04 AM -07:00