postgresql数据库3种程序（rule,trigger ,FUNCTION ）

1.

CREATE [ OR REPLACE ] RULE name AS ON event

TO table_name [ WHERE condition ]

DO [ ALSO | INSTEAD ] { NOTHING | command | ( command ; command ... ) }

2.

CREATE  TRIGGER trigger_name [BEFORE|AFTER|INSTEAD OF] event_name
ON table_name
[
 -- Trigger logic goes here....
];  

3.

CREATE [OR REPLACE] FUNCTION function_name (arguments)
RETURNS return_datatype AS $variable_name$
  DECLARE
    declaration;
    [...]
  BEGIN
    < function_body >
    [...]
    RETURN { variable_name | value }
  END; LANGUAGE plpgsql;