RE: Need another pair(s) of eyes
- From: "Igor Neyman" <ineyman@xxxxxxxxxxxxxx>
- To: <breitliw@xxxxxxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 26 Jul 2007 08:54:20 -0400
So, which one performs better?
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Wolfgang Breitling
Sent: Thursday, July 26, 2007 6:22 AM
To: oracle-l
Subject: Need another pair(s) of eyes
Hi,
or probably more accurately a few more brains.
I think the following are equivalent:
do something (select, update, delete)
where < some predicates>
and exists ( select 'x' from tableA, tableB
where < some regular predicates > and < some correlated predicates >
UNION ALL
select 'x' from tableC, tableD (could be same as A and/or B)
where < some regular predicates > and < some correlated predicates >
)
and
do something (select, update, delete)
where < some predicates>
and ( exists ( select 'x' from tableA, tableB
where < some regular predicates > and < some correlated predicates >
)
OR exists (
select 'x' from tableC, tableD (could be same as A and/or B)
where < some regular predicates > and < some correlated predicates >
)
)
Likewise for not exists:
do something (select, update, delete)
where < some predicates>
and not exists ( select 'x' from tableA, tableB
where < some regular predicates > and < some correlated predicates >
UNION ALL
select 'x' from tableC, tableD (could be same as A and/or B)
where < some regular predicates > and < some correlated predicates >
)
vs.
do something (select, update, delete)
where < some predicates>
and not exists ( select 'x' from tableA, tableB
where < some regular predicates > and < some correlated predicates >
)
AND not exists (
select 'x' from tableC, tableD (could be same as A and/or B)
where < some regular predicates > and < some correlated predicates >
)
Can someone think of some condition(s), examples where they would not be
equivalent?
Regards
Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
AIM: WBreitling
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