In the first case you are testing for equality against NULL.=20
Niall Litchfield
Oracle DBA
Audit Commission
+44 117 975 7805=20
> -----Original Message-----
> From: jreyes_at_dazasoftware.com=20
> Sent: 20 February 2004 14:32
> To: aore_at_dazasoftware.com; cmonroy_at_dazasoftware.com;=20
> dpuna_at_dazasoftware.com; dvenegas_at_dazasoftware.com;=20
> ilujan_at_dazasoftware.com; jdaza_at_dazasoftware.com;=20
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> Subject: IN ignore null values=20
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> An interesting observation
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> IN ignore null values as you can see in the table there are=20
> 310 null values
> in column TBL_DSM.
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> SQL> select count(*) from daz.utl_tablas_me
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> 2 where tbl_dsm in
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> 3 (select null from daz.utl_tablas_me);
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> COUNT(*)
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> ---------
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> 0
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> SQL> select count(*) from daz.utl_tablas_me
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> 2 where exists(select null from daz.utl_tablas_me);
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> COUNT(*)
>=20
> ---------
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> 310
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Received on Fri Feb 20 2004 - 08:47:09 CST
