Can I use select inside a select??? If so how?

Paingiver · #1 (**permalink**) 08-25-06, 06:14

The select that I want using is like this....
Select (Select * from Databasename where Columnname = 'Value1' and Column2 is not null) from Databasename where Columnname <> 'Value'

DB2 version 8 I think

Thanks

Paingiver · #2 (**permalink**) 08-25-06, 06:28

I want to get value that have some complex condition like if Columnname = 'Value1' then Column2 is not null is the bellow sql possible?

Select * from Databasename where Columnname <> 'Value' and (if Columnname = 'Value1' then Column2 is not null)

Thanks

umayer · #3 (**permalink**) 08-25-06, 08:32

How about:

Select *
from Databasename
where Columnname <> 'Value' and
(Columnname = 'Value1' and Column2 is not null or Columnname ^= 'Value1' )

Peter.Vanroose · #4 (**permalink**) 08-25-06, 14:58

Quote:

Originally Posted by umayer

Select *
from Databasename
where Columnname <> 'Value' and
(Columnname = 'Value1' and Column2 is not null or Columnname ^= 'Value1')

Somewhat shorter:

Code:

Select * 
from   Databasename 
where  Columnname <> 'Value'
  and  (Column2 is not null or Columnname <> 'Value1')

This is a general logic conversion rule:
"if A then B" is equivalent with "(not A) or B".

Paingiver · #5 (**permalink**) 08-26-06, 08:49

Thanks for the replys.

grofaty · #6 (**permalink**) 08-28-06, 07:38

Hi,

if you would like to write select inside select you can write:
Select from (Select * from Databasename where Columnname = 'Value1' and Column2 is not null) as temp where Columnname <> 'Value'

Hope this helps,
Grofaty

umayer · #7 (**permalink**) 08-28-06, 08:24

Quote:

Originally Posted by grofaty

Select from (Select * from Databasename where Columnname = 'Value1' and Column2 is not null) as temp where Columnname <> 'Value'

I disagree.

The correct nested table expression is:

Select from (Select * from Databasename where Columnname ^= 'Value1' or Column2 is not null) as temp where Columnname <> 'Value'

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