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Joining Two Select statements

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Topic

wisdomtree
Starting Member

1 Post

Posted - 2008-10-20 : 04:11:15

Hi I have come across a similar query which was written by my previous db developer. can any one explain how does this work and when should i use such query

select * from
(select a.x1,a.x2,.. from t1) a
inner join
(select b.x1,b,x2 from t2) b
on (a.x1=b.x2)

i am not sure whether the above code i wrote is right but hope it gives you an idea about what i am asking.
Please help me out by giving some example so that i will be able to understand

rgs
bhanu

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-10-20 : 04:13:39

its right. only problem is it wont need alises inside as aliases are defined for derived tables and wont be available inside

select * from
(select x1,x2,.. from t1) a
inner join
(select x1,x2 from t2) b
on (a.x1=b.x2)

madhivanan
Premature Yak Congratulator

22864 Posts

Posted - 2008-10-20 : 04:17:10

or

select a.columns,b.columns from t1 as a inner join t2 as b on (a.x1=b.x2)

Madhivanan

Failing to plan is Planning to fail

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-10-20 : 04:47:33

quote:
Originally posted by madhivanan

or

select a.columns,b.columns from t1 as a inner join t2 as b on (a.x1=b.x2)

Madhivanan

Failing to plan is Planning to fail

this is prefered way to do unless you dont have any specific calculations/dervivations to done on a any table column before joining.

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