数据库完整性

触发器

CREATE TRIGGER insert_Sal
AFTER INSERT ON Teacher
FOR EACH ROW
AS BEGIN
  IF (new.Sal <> old.Sal) THEN INSERT INTO Sal_log VALUES 
    (new.Eno, new.Sal, CURRENT_USER, CURRENT_TIMESTAMP);
  END IF;
END

上例中使用到了new和old，这是两个元组，而在SQL server中的T-SQL中是inserted和deleted两张表。

CREATE OR REPLACE TRIGGER trl
AFTER UPDATE OR INSERT OR DELETE