NOTIFY SQL - Language Statements NOTIFY Signals all frontends and backends listening on a class 1998-09-24 NOTIFY classname 1998-09-24 classname Table or arbitrary relation class used for notification. 1998-09-24 status NOTIFY Notification message from backend. 1998-09-24 NOTIFY is used to awaken all sessions which have previously executed LISTEN classname. This can be used either within an instance-level rule as part of the action body or from a normal query. When used from within a normal query, this can be thought of as interprocess communication (IPC). When used from within a rule, this can be thought of as an alert mechanism. Note that the mere fact that a NOTIFY has been executed does not imply anything in particular about the state of the class (e.g., that it has been updated), nor does the notification protocol transmit any useful information other than the class name. Therefore, all NOTIFY does is indicate that some backend wishes its peers to examine classname in some application-specific way. In fact, classname need not be the name of an SQL class at all. It is best thought of as a condition name that the application programmer selects. This event notification is performed through the libpq protocol and frontend application interface. The application program must call the routine PQnotifies in order to find out the name of the class to which a given notification corresponds. If this code is not included in the application, the event notification will be queued and never be processed. 1998-09-24 -- Configure and execute a listen/notify sequence -- from psql CREATE TABLE t (i int4); LISTEN t; NOTIFY t; NOTIFY ASYNC NOTIFY of 't' from backend pid '10949' received 1998-09-24 There is no NOTIFY statement in SQL92.