ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
SQL support in local databases
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.
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.
Last updated 6/6/2012
1103