Article View: borland.public.interbase.sql
Article #466Re: Performance issue of group by clause.
From: Craig Stuntz TeamB
Date: Thu, 29 Nov 2007 13:18
Date: Thu, 29 Nov 2007 13:18
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2160 bytes
Monalee Bhandge wrote: > Even I create index on dr_amt, cr_amt, acc_name columns then also > I doesn't get that much speed. No, it won't, because indices tend to make GROUP BY slower. GROUP BY orders the result set, then returns selected rows while computing aggregates. An index typically makes returning an ordered result set *slower.* OTOH, an index on acc_name might help reduce the number of rows which must be examined (presuming that there are > 4 values of acc_name in the real data, that is). > In this table there are 90,00000 rows. I'm not sure what this means. I don't recognize that as a number. What is the actual problem you are trying to solve? -- Craig Stuntz [TeamB] � Vertex Systems Corp. � Columbus, OH Delphi/InterBase Weblog : http://blogs.teamb.com/craigstuntz Everything You Need to Know About InterBase Character Sets: http://blogs.teamb.com/craigstuntz/articles/403.aspx
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X-Google-Thread: 114a0e,5460ac00bbec9e3 X-Google-Attributes: gid114a0e,public,usenet X-Google-Language: ENGLISH,ASCII From: "Craig Stuntz [TeamB]" <craig_stuntz@nospam.please [a.k.a. acm.org]> Subject: Re: Performance issue of group by clause. Newsgroups: borland.public.interbase.sql References: <474eb557$1@newsgroups.borland.com> Organization: Vertex Systems Corporation User-Agent: XanaNews/1.18.1.9 X-Face: "huzh55Xi]!ZNni78>a*5+).`SK?<^q2MlHk-C]Z2M9T@\J5ZCB$95Ey+s"XQuhGFA[eutZ:0^AV!Q;t>gE`1-=8d;HZ6~*o1dH<X9\b$!|(}+I'!Xq)@3Op}%0ArW&nf'Qh*EwR MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit NNTP-Posting-Host: 64.199.116.234 Message-ID: <474eca51$1@newsgroups.borland.com> Date: 29 Nov 2007 06:18:57 -0700 X-Trace: newsgroups.borland.com 1196345937 64.199.116.234 (29 Nov 2007 06:18:57 -0700) Lines: 27 X-Authenticated-User: cstuntz Path: arc1-ca.pugleaf.net!g2news1.google.com!news2.google.com!eweka.nl!lightspeed.eweka.nl!feeder3.cambrium.nl!feeder2.cambrium.nl!feeder6.cambrium.nl!feed.tweaknews.nl!xlned.com!feeder1.xlned.com!newsfeed.freenet.de!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsgroups.borland.com!not-for-mail