Oracle PL/SQL Programming: A Developer's Workbook

Chapter 16. Triggers

A trigger is a special PL/SQL procedure that fires, or executes, in response to a specific triggering event. For example, you might write a trigger to enforce a business rule on INSERT statements on a particular table, maintain referential integrity in a distributed database, or track user logons. A trigger has three parts:

• A header line that defines the triggering event

• An optional WHEN clause that restricts the trigger’s firing to a specific condition (for example, the trigger fires only when salary is greater than $50,000)

• The actual trigger code itself

This chapter tests your ability to define triggers for a variety of events, work with correlation variables (special pseudo-column names that represent things like the old and new values of a column), and use triggers to implement business logic.

Beginner

16-1.	What is a trigger?
16-2.	For which of the following events can you create a trigger? An INSERT, UPDATE, or DELETE statement on a specific object An execution of a specific procedure A user logon (or logoff) A DDL statement, such as DROP or ALTER, on a specific object
16-3.	What is one of the main differences between the execution of a trigger and the execution of a stored procedure?
16-4.	What are the two modes a trigger can have?
16-5.	Which of the following terms describes the situation in which the execution of one trigger results in the execution of another, or possibly more, different triggers? Trigger torrent Cascading triggers Chain reaction Interlock Recursive nesting ...