RE: NOT IN with NULL-values

Frank,

"A NOT IN evaluates to FALSE if *any* member of the set is NULL".

http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/ a85397/operator.htm#1003933

Also scroll up just a tad on that link and look at the comments for NOT IN in table 3.4. This is a subtlety that many folks overlook until it bites them on the tail.

With regards to your NOT EXISTS, you didn't include correlation between the two tables (which Amar pointed out with the example). Try this:

SQL> select * from fk_ldm1 a
  2 where not exists (select * from fk_ldm2 b where a.id = b.id);

        ID

         3

For each row in fk_ldm1 the sub-query is evaluated. And since you did not include correlation, the sub-query will always return a row(s) (there's no criteria on it), thus making the NOT EXISTS condition FALSE for each row in fk_ldm1.

Regards,

Larry G. Elkins
elkinsl_at_flash.net
214.954.1781

> -----Original Message-----
> From: root_at_fatcity.com [mailto:root_at_fatcity.com]On Behalf Of Kuijten, F.
> (Frank)
> Sent: Monday, October 29, 2001 8:35 AM
> To: Multiple recipients of list ORACLE-L
> Subject: RE: NOT IN with NULL-values
>
>
> Amar,
>
> Thanks.
>
> One question : Do you have a NULL value in the 'am91' table ?
>
> Because that's where my problem is.
> Without the NULL value, all queries are giving the expected results.
>
>
> Greetings,
> Frank
>

-- 
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Author: Larry Elkins
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