回复：我也跟风问个关于SQL的问题，请高人赐教。

1)Select ….
From DB1 inner join DB2 on a.keyword=b.keyword
Where controls;
Quit;


2)Select ……
From DB1 where controls and keyword in ( select keyword from B );

a) 1) and 2) are not same when select clause include columns in DB2

b) if select keyword from B return large dataset 2) will be slower then 1)

c)you can use select distinct keyword from B if there are duplicates return from this query

所有跟帖： 

• 回复：回复：我也跟风问个关于SQL的问题，请高人赐教。 -veggiedoggie- ♀ (246 bytes) () 11/10/2009 postreply 11:14:50

• 回复：回复：回复：我也跟风问个关于SQL的问题，请高人赐教。 -nice2u- ♂ (278 bytes) () 11/10/2009 postreply 11:26:14