TRIGGERS IN PL/SQL
The literal meaning of the word "Trigger" is to activate. Triggers are simply stored procedures that are ran automatically by the database whenever some event (usually a table update) happens.
"A Trigger is a stored procedure that defines an action that the database automatically initiates when some database-related event such as INSERT, UPDATE or DELETE occurs."
Thus the triggers are basically PL/SQL procedures that are
tables, and are called whenever a certain modification (event) modification
statements may include INSERT, UPDATE, and
Syntax:
CREATE [OR REPLACE] TRIGGER
trigger_name BEFORE (or AFTER) INSERT OR UPDATE [OF COLUMNS] OR DELETE ON table
name [FOR EACH ROW [WHEN (condition)]] BEGIN.
...
END;
By the usual CREATE OR REPLACE the TRIGGER specifies just
what type of object is being created.
The BEFORE (or AFTER) in the trigger definition refers to
when one wants to run the trigger, either before the actual database
modification (update, delete, insert) or after.
