盡量先過濾數據再進行表連接，

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

?

改為 select a

　　 from (select * from tbluser where tbluser.id=4) as tblUser

????? inner join tblShop on tblUser.id=tblShop.id

　　inner join tblThing on tblUser.id=tblThing.id

?

?

?

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