postgresql触发器使用实例

创建测试表：
CREATE TABLE emp (
empname text NOT NULL,
salary integer
);

CREATE TABLE emp_audit(
operation text NOT NULL,
stamp timestamp NOT NULL,
userid text NOT NULL,
empname text NOT NULL,
salary integer
);

创建存储过程：
CREATE OR REPLACE FUNCTION process_emp_audit()
RETURNS TRIGGER AS
$emp_audit$
BEGIN
    IF (TG_OP = 'DELETE') THEN
        INSERT INTO emp_audit SELECT 'DELETE', now(), user, OLD.*;
    ELSIF (TG_OP = 'UPDATE') THEN
        -- save old and new values
        INSERT INTO emp_audit SELECT 'OLD', now(), user, OLD.*;
        INSERT INTO emp_audit SELECT 'NEW', now(), user, NEW.*;
    ELSIF (TG_OP = 'INSERT') THEN
        INSERT INTO emp_audit SELECT 'INSERT', now(), user, NEW.*;
    ELSEIF (TG_OP = 'TRUNCATE') THEN
        INSERT INTO emp_audit SELECT 'TRUNCATE', now(), user, '-', -1;
    END IF;
    RETURN NULL; -- result is ignored bacause this is an AFTER trigger
END;
$emp_audit$ LANGUAGE plpgsql;

创建针对insert和update每行的触发器：

CREATE TRIGGER emp_audit
AFTER INSERT OR UPDATE OR DELETE ON emp
FOR EACH ROW EXECUTE PROCEDURE process_emp_audit();

创建针对update的语句级的触发器：

CREATE TRIGGER emp_audit_truncate
AFTER TRUNCATE ON emp
FOR EACH STATEMENT EXECUTE PROCEDURE process_emp_audit();