触发器(Trigger)是用户定义在关系表上的一类由事件驱动的特殊过程。一旦定义,任何用户对表的增、删、改操作均由服务器自动激活相应的触发器,在DBMS核心层进行集中的完整性控制。它是一种特殊类型的存储过程,它在指定的表中的数据发生变化时自动生 Triggers are a type of event-driven, special process that users define on relational tables. Once defined, any user on the table by delete, delete, modify the operation by the server automatically activate the appropriate trigger, in the DBMS core for centralized integrity control. It is a special type of stored procedure that automatically generates data in a specified table when it changes