Oracle SQL: the Essential Reference

7.7. Triggers

A trigger represents a special type of PL/SQL block that you can tie to an event. When a trigger is executed by the Oracle database, it is said to "fire." The most commonly used types of triggers are Data Manipulation Language (DML) triggers that fire in response to INSERT, UPDATE, and DELETE statements. There are 15 different DML trigger types, listed in Table 7-9.

Table 7-9. Oracle's DML Trigger Types

Trigger Event	Triggered for Each	Description
BEFORE INSERT	Statement	Executes code before an INSERT statement is executed on the target table
BEFORE INSERT	Row	Executes code before each row is INSERTed into the target table
AFTER INSERT	Statement	Executes code after an INSERT statement is executed on the target table
AFTER INSERT	Row	Executes code after each row is INSERTed into the target table
INSTEAD OF INSERT	Row	Executes code instead of the INSERT for each row on which an INSERT is attempted
BEFORE UPDATE	Statement	Executes code before an UPDATE statement is executed on the target table
BEFORE UPDATE	Row	Executes code before each row of the target table is UPDATEd
AFTER UPDATE	Statement	Executes code after an UPDATE statement is executed on the target table
AFTER UPDATE	Row	Executes code after each row of the target table is UPDATEd
INSTEAD OF UPDATE	Row	Executes code instead of the UPDATE statement for each row for which an UPDATE is attempted
BEFORE DELETE	Statement	Executes code before a DELETE statement is executed on the target table
BEFORE DELETE	Row ...