回複:我也跟風問個關於SQL的問題,請高人賜教。

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: 

請您先登陸,再發跟帖!