Trigger VS Procedure

今天，碰到一个Procedure的问题，刚好一个同事提出了一个疑问，为什么不用Trigger，Trigger这么好用。

第一反应，这个问题很奇怪，通常只把Procedure与在APP中执行的SQL文作区别。个人脑海里，Trigger是

用于触发事件用，与某个表的相关动作进行关联。

从各个角度，似乎关系不大，但是又有所关联，扯不开关系。

纯理论上考虑，二者的区别可以简单描述如下：

1.Trigger是被绑定到某个具体的Table的更新，删除，插入的动作中；而Procedure则是DataBase中的一个

公用方法， 可以被任意调用。

2.Trigger的管理相对隐蔽，而Procedure则相当明了直接。后期维护管理上，显然Procedure更容易些。

一旦Trigger被绑定，无论是后期维护认为更改对象数据，也将触发关联Trigger。产生一些意想不到的问题。

很多人，基本设计者基本不考虑采用Trigger。

 综合看来，Procedure用途显然更广泛也更受欢迎，但为什么微软要增加Trigger的功能？笔者认为这是一个

思维模式，和编成相通。可以说微软的偏好。

如在C#中，我们既可以用共通方法（Public Method），也可用通过共通事件 （EVENT）来处理相关。而者

有区别，也有共通点。如何理解二者的区别似乎也可对等的看待Trigger和Procedure的区别。

1. We can execute a stored procedure whenever we want with the help of the exec command, but a trigger can only be executed whenever an event (insert, delete, and update) is fired on the table on which the trigger is defined.
2. We can call a stored procedure from inside another stored procedure but we can't directly call another trigger within a trigger. We can only achieve nesting of triggers in which the action (insert, delete, and update) defined within a trigger can initiate execution of another trigger defined on the same table or a different table.
3. Stored procedures can be scheduled through a job to execute on a predefined time, but we can't schedule a trigger.
4. Stored procedure can take input parameters, but we can't pass parameters as input to a trigger.
5. Stored procedures can return values but a trigger cannot return a value.
6. We can use Print commands inside a stored procedure for debugging purposes but we can't use print commands inside a trigger.
7. We can use transaction statements like begin transaction, commit transaction, and rollback inside a stored procedure but we can't use transaction statements inside a trigger.
8. We can call a stored procedure from the front end (.asp files, .aspx files, .ascx files, etc.) but we can't call a trigger from these files.
9. Stored procedures are used for performing tasks. Stored procedures are normally used for performing user specified tasks. They can have parameters and return multiple results sets.
10. The Triggers for auditing work: Triggers normally are used for auditing work. They can be used to trace the activities of table events.

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