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SQL Anywhere 11.0.0 » SQL Anywhere Server - SQL Usage » SQL Dialects and Compatibility » Other SQL dialects » Transact-SQL procedure language overview

 

Transact-SQL trigger overview

Trigger compatibility requires compatibility of trigger features and syntax. This section provides an overview of the feature compatibility of Transact-SQL and SQL Anywhere triggers.

Adaptive Server Enterprise supports statement-level AFTER triggers; that is, triggers that execute after the triggering statement has completed. SQL Anywhere supports row-level BEFORE, AFTER, and INSTEAD OF triggers, and statement-level AFTER and INSTEAD OF triggers. See Introduction to triggers.

Row-level triggers are not part of the Transact-SQL compatibility features, and are discussed in Using procedures, triggers, and batches.

Description of unsupported or different Transact-SQL triggers

Features of Transact-SQL triggers that are either unsupported or different in SQL Anywhere include:

  • Triggers firing other triggers   Suppose a trigger performs an action that would, if performed directly by a user, fire another trigger. SQL Anywhere and Adaptive Server Enterprise respond slightly differently to this situation. By default in Adaptive Server Enterprise, triggers fire other triggers up to a configurable nesting level, which has the default value of 16. You can control the nesting level with the Adaptive Server Enterprise nested triggers option. In SQL Anywhere, triggers fire other triggers without limit unless there is insufficient memory.

  • Triggers firing themselves   Suppose a trigger performs an action that would, if performed directly by a user, fire the same trigger. SQL Anywhere and Adaptive Server Enterprise respond slightly differently to this situation. By default, in SQL Anywhere, non-Transact-SQL triggers fire themselves recursively, whereas Transact-SQL dialect triggers do not fire themselves recursively. However, for Transact-SQL dialect triggers, you can use the self_recursion option of the SET statement [T-SQL] to allow a trigger to call itself recursively. See SET statement [T-SQL].

    By default in Adaptive Server Enterprise, a trigger does not call itself recursively, but you can use the self_recursion option to allow recursion to occur.

  • ROLLBACK statement in triggers   Adaptive Server Enterprise permits the ROLLBACK TRANSACTION statement within triggers, to roll back the entire transaction of which the trigger is a part. SQL Anywhere does not permit ROLLBACK (or ROLLBACK TRANSACTION) statements in triggers because a triggering action and its trigger together form an atomic statement.

    SQL Anywhere does provide the Adaptive Server Enterprise-compatible ROLLBACK TRIGGER statement to undo actions within triggers. See ROLLBACK TRIGGER statement.