$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.18 2001/11/19 03:58:25 tgl Exp $

The trigger can be specified to fire either before BEFORE the

operation is attempted on a tuple (before constraints

are checked and the <command>INSERT</command>, <command>UPDATE</command> or

<command>DELETE</command> is attempted) or

AFTER the operation has been attempted (e.g., after constraints

are checked and the <command>INSERT</command>,

<command>UPDATE</command> or <command>DELETE</command> has

completed). If the

trigger fires before the event, the trigger may

skip the operation for the current tuple, or change the tuple

being inserted (for <command>INSERT</command> and

<command>UPDATE</command> operations only). If

the trigger fires after the event, all changes, including the

last insertion, update, or deletion, are <quote>visible</quote> to the trigger.