关于mysql触发器根据条件更新的问题!

Question

a表:

id (key)
deviceid
devicename
brand 

b表:

 id (key)
deviceid(key)联合主键
devicename
brand 

请问如何才能做到到b表插入deviceid时，如果a.deviceid=b.deviceid则更新b.devicename and b.brand
我的写法是

BEGIN
UPDATE b SET 
devicename = new.devicename,
brand = new.brand
WHERE deviceid  = (SELECT deviceid FROM a WHERE  brand = new.brand and devicename = new.devicename and brand = new.brand );

但是这样不对，请问大神改怎么做？

Answer 1

http://blog.csdn.net/lovelichao12/article/details/76680214