FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: Steven Orton [mailto:sorton9999 AT usa.net]
> Sent: January 8, 2004 1:57 PM
> 
>   I seem to be having problems with the following query:
> 
>   SELECT * FROM table1 WHERE Target_ID=(SELECT DISTINCT 
> Target_ID FROM table2
> WHERE PlatformTypeID=62 AND db_ctx_id=3)

It's not a good idea to rely on a subquery returning only one row to a point
evaluation.  How do you expect the server to cope if it returns two
(distinct) Target_IDs?  

I would do:

SELECT * FROM table1 
WHERE Target_ID in (
        SELECT DISTINCT Target_ID 
        FROM table2
        WHERE PlatformTypeID=62 
        AND db_ctx_id=3
        )

or, ensure the subquery really really returns only one row, viz:

SELECT * FROM table1 
WHERE Target_ID = (
        SELECT min(Target_ID) 
        FROM table2
        WHERE PlatformTypeID=62 
        AND db_ctx_id=3
        )

The right choice depends on the situation.  

HTH.  :-)

--jkl
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