进一步理解触发器原理！！！！

二个表ORDERS和ORDER  DETAIL

算法如下：在我更新ORDER DETAIL时，一起更新ORDERS，用触发器实现如下：

------------插入操作时 

CREATE TRIGGER intOrderdetail

ON [ORDER DETAILS]

FOR INSERT AS

update orders

set SUM_MONEY=SUM_MONEY+unitprice*quantity*(1-discount)

 from orders s, inserted ins

 where s.orderid=ins.orderid

 

 

 ---------------UPDATE操作时(分两步DELETED和INSERTED)

CREATE TRIGGER updOrderdetail

ON [ORDER DETAILS]

FOR update AS

 

update orders

set SUM_MONEY=SUM_MONEY-unitprice*quantity*(1-discount)

 from orders s, deleted del

 where s.orderid=del.orderid

update orders set SUM_MONEY=SUM_MONEY+unitprice*quantity*(1-discount)

 from orders s, inserted ins

 where s.orderid=ins.orderid

 

 

 

 

 --------删除操作时

CREATE TRIGGER delOrderdetail

ON [ORDER DETAILS]

FOR DELETE AS

update orders set SUM_MONEY=SUM_MONEY-unitprice*quantity*(1-discount)

 from orders s, deleted del

 where s.orderid=del.orderid

关于ROLE，要删除角色时，必须除去它属于的用户才可以删除它。