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Home -> Community -> Mailing Lists -> Oracle-L -> RE: minus vs. where not exists, vs. where not in
well superman is poorer than batman
-----Original Message-----
Sent: 22 September 2003 13:45
To: Multiple recipients of list ORACLE-L
Yeah, Superman had Super powers. Batman just relied on a bunch of gadgets.
Of course my original post was implying the classic "it depends". There are some scenario's where a specific approach is faster than the other and there are some scenario's where it doesn't matter because oracle can rewrite the query effectively anyway. What does matter - "If in doubt test it out".
"Sinardy Xing"
<SinardyXing_at_bkgc To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
omsvc.com> cc:
Sent by: Subject: RE: minus vs. where not exists, vs. where not in
ml-errors_at_fatcity
.com
22/09/2003 15:29
Please respond to
ORACLE-L
I think Superman is stroger than Batman
-----Original Message-----
Sent: 22 September 2003 08:30
To: Multiple recipients of list ORACLE-L
I'm not sure that there is a good answer to that question. The question
sounds like the dilemma: who's stronger, Batman or Superman?
Unfortunately, superheroes do not exist, so we cannot have a real life
comparison. It is exactly the same with not exists vs. minus. Comparisons
make
sense only within a real life application in a real configuration, that is
why both mechanisms are provided. Sort_area_size does influence
performance,
unless memory is slow, system is swapping or something else.
In the world of superheroes, my favorite is Alice and her "fist of death".
On 2003.09.21 19:54, Mark Richard wrote:
>
> I don't have any scientific proof but I imagine the sort_area_size could
be
> different between "not exists" and "minus". When doing "minus" the
entire
> select string would have to be compared for equality, which could be very
> large depending on your string.
>
> Minus is probably an easier way (at least from a coding perspective) of
> comparing every column in a table, or incorporating complexity in the
> select statement.
>
> Having said that. Each statement has it's pros and cons and I guess it
> depends on the volume of the various queries, etc. For example, if the
> have table A with 5 rows and table B with 1000000 rows executing "select
> a.field from a where not exists (select 1 from b where b.field = a.field)
> will result in 5 quick searches (assuming b.field is indexed) whereas
> "select a.field from a where a.field not in (select b.field from b)" will
> result in a full index read of b, as would "select a.field from a minus
> select b.field from b". Obviously different queries and different
volumes
> will tip the scales in different directions.
>
> Regards,
> Mark.
>
>
>
>
>
> "Ryan"
>
> <rgaffuri_at_cox.net To: Multiple
recipients
> of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > cc:
>
> Sent by: Subject: minus vs. where
not
> exists, vs. where not in
> ml-errors_at_fatcity
>
> .com
>
>
>
>
>
> 22/09/2003 03:59
>
> Please respond to
>
> ORACLE-L
>
>
>
>
>
>
>
>
>
> Do any of you have any cases when minus is superior in performance? Ive
> found 'not in' with a hash_aj to be the best option if the sub-query is
> significantly less 'costly' then the outer query. I dont mean cost in
terms
> of the Explain Plan, I mean the work Oracle has to do to find a result
set.
> It also depends on a proper hash_area_size
>
> I find 'where not exists' to be best if the subquery is relatively close
in
> cost to the outer query. Yes I know you cant make broad generalizations,
> but there has to be some 'narrow' generalizations you can make. Such as
> certain cases, etc...
>
> what have you seen? There seems to be very little work in this area in
the
> literature.
>
> Does 'where not exist' need more or less sort_area_size space than minus?
>
>
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Mark Richard
> INET: mrichard_at_transurban.com.au
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-- Mladen Gogala Oracle DBA -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: mgogala_at_adelphia.net Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Sinardy Xing INET: SinardyXing_at_bkgcomsvc.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Privileged/Confidential information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and kindly notify the sender by reply e-mail or by telephone on (61 3) 9612-6999. Please advise immediately if you or your employer does not consent to Internet e-mail for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of Transurban City Link Ltd shall be understood as neither given nor endorsed by it. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Privileged/Confidential information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such a case, you should destroy this message and kindly notify the sender by reply e-mail or by telephone on (03) 9612-6999 or (61) 3 9612-6999. Please advise immediately if you or your employer does not consent to Internet e-mail for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of Transurban Infrastructure Developments Limited and CityLink Melbourne Limited shall be understood as neither given nor endorsed by them. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mark Richard INET: mrichard_at_transurban.com.au Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Sinardy Xing INET: SinardyXing_at_bkgcomsvc.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Mon Sep 22 2003 - 05:24:35 CDT
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