Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 1 Thursday, March 12, 12:30 – 13:30PM. MIDTERM

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Triggers A trigger is a statement that is executed automatically by the system as a side effect of a modification to the database. To design a trigger mechanism, we must: –Specify the conditions under which the trigger is to be executed. –Specify the actions to be taken when the trigger executes. Introduced to SQL standard in SQL:1999, Supported even earlier using non-standard syntax by most DBMSes. –Syntax illustrated here is for Oracle 11g.

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Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 13 Triggers are commonly used to monitor events occurring in a database. AFTER Triggers

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Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 17 Triggers for Views Recall updateable views?

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Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 21 Triggers on DDL Statements What’s a DDL statement?

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Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 24 Disable/Enable Triggers Why would I want to disable a trigger?

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Murach’s Oracle SQL and PL/SQL, C16© 2014, Mike Murach & Associates, Inc.Slide 27 Compound Triggers Why do we need another type of trigger? It solves an well-known problem in Oracle. Contains code that executes: BEFORE the triggering statement executes. BEFORE the row is modified. AFTER the row is modified. AFTER the triggering statement has finished.

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