Trigger in PL/SQL

Trigger is invoked by Oracle engine automatically whenever a specified event occurs.Trigger is stored into database and invoked repeatedly, when specific condition match.

Triggers are stored programs, which are automatically executed or fired when some event occurs.

Triggers are written to be executed in response to any of the following events.

A database manipulation (DML) statement (DELETE, INSERT, or UPDATE).

A database definition (DDL) statement (CREATE, ALTER, or DROP).

A database operation (SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN).

Triggers could be defined on the table, view, schema, or database with which the event is associated.

Advantages of Triggers

These are the following advantages of Triggers:

• Trigger generates some derived column values automatically

• Enforces referential integrity

• Event logging and storing information on table access

• Auditing

• Synchronous replication of tables

• Imposing security authorizations

• Preventing invalid transactions

Now that you completed tutorial, you can also revise it with important questions and answers in PL/SQL

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