Signaling Event Occurrences
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A trigger or stored procedure must signal the occurrence of an event, usually a database change such as an INSERT
, UPDATE
, or DELETE
, by using the POST_EVENT
statement. POST_EVENT
alerts the event manager to the occurrence of an event after a transaction is committed. At that time, the event manager passes the information to registered applications.
A trigger or stored procedure that posts an event is sometimes called an event alerter. For example, the following isql
script creates a trigger that posts an event to the event manager whenever any application inserts data in a table:
CREATE TRIGGER POST_NEW_ORDER FOR SALES ACTIVE AFTER INSERT POSITION 0 AS BEGIN POST_EVENT 'new_order'; END ;
Event names have no character size restrictions.
POST_EVENT
is a stored procedure and trigger language extension, available only within stored procedures and triggers.For a complete discussion of writing a trigger or stored procedure as an event alerter, see the Data Definition Guide.