摘要:
尽量先过滤数据再进行表连接,例如:select a from tblUser inner join tblShop on tblUser.id=tblShop.id inner join tblThing on tblUser.id=tblThing.id where tblUser.id=4改为 select a from (select * from tblu... 阅读全文
posted @ 2010-05-07 18:01 Learn more 阅读(113) 评论(0) 推荐(0) 编辑