Oracle PL/SQL Programming: A Developer's Workbook

Chapter 16. Triggers

Beginner

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16-1.	A trigger is a block of code (whether in PL/SQL, Java, or C) that fires, or executes, in response to a specific event.
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16-2.	The statements are: True. You can create a trigger in response to most Data Manipulation Language (DML) operations. False. There is no AFTER EXECUTION. True. Oracle8i allows you to trap “user-level” events such as logons. True. Oracle8i allows you to create triggers that fire when Data Definition Language (DDL) statements are executed.
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16-3.	A trigger executes implicitly in response to an event, such as an update to a table. A procedure executes explicitly at the request of a user (or a call from another program).
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16-4.	A trigger can have one of two modes: ENABLED (meaning that it fires normally) and DISABLED (meaning that it does not fire, even if its triggering event occurs).
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16-5.	(b). A trigger that causes other triggers to fire is called a cascade.
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16-6.	Statement-level triggers fire only one time per statement, and row-level triggers fire for each row that is affected by the DML statement.
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16-7.	The WHEN clause causes a trigger to fire only when a specific set of user-defined conditions are met.
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16-8.	Trigger (b) correctly populates the employee_id column. Trigger (a), which attempts to set the sequence number using an INSERT statement, illustrates a fairly common mistake. While Trigger (a) compiles successfully, it will probably produce the following error when it’s executed: ORA-00036: Maximum number of recursive sql ...