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Article #5211Re: Clarification on AutoInc fields
From: Giuliano
Date: Wed, 04 Jul 2001 21:40
Date: Wed, 04 Jul 2001 21:40
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2066 bytes
On Wed, 4 Jul 2001 22:31:34 +0200, "Umberto Uderzo" <umberto@uderzo.it> wrote: >Sure your suggestion will improve the performance. >Anyway i think that a COUNT(*) on a decent DBMS will not decrease so much >the performance, since this is a particular query (DBMS should mantain tha >record count of a table i think). Sure, a RDBMS could treat the count(*) on tables in special manner in order to improve the performance, but if you have a query with joins (or a where clause with non trivial expression exists) this still wouldn't to be so true. For example, a count(*) using a where clause that involves a column that isn't indexed, at the best, would to imply a linear reading of all rows in order to determine what's the resulting set. In fact, like user of the RDBMS (the client generating the request to RDBMS), you wouldn't be able to know if you are doing a count(*) with a real table or with a view using, for example, one or more medium / complex joins. My 2 cents Ciao! Giuliano
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 10698b,2eab2f6830ef7732 X-Google-Attributes: gid10698b,public X-Google-ArrivalTime: 2001-07-04 14:50:37 PST From: gcardinali@remove.adhoc.net (Giuliano) Newsgroups: borland.public.cppbuilder.database.ado Subject: Re: Clarification on AutoInc fields Date: Wed, 04 Jul 2001 21:40:30 GMT Message-ID: <3b448816.363089384@newsgroups.borland.com> References: <3b3b532b$1_2@dnews> <3B3BD2D2.5F446F35@temporaldoorway.com> <3b3c3ad2_1@dnews> <3b3c7c38_1@dnews> <3b40f10e_2@dnews> <3b42e1b1_2@dnews> <3b437c61_2@dnews> X-Newsreader: Forte Agent 1.5/32.451 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 194.183.65.61 X-Trace: dnews 994283128 194.183.65.61 (4 Jul 2001 14:45:28 -0700) Lines: 24 Path: arc1-ca.pugleaf.net!archiver1.google.com!newsfeed.google.com!sn-xit-02!supernews.com!newsfeed.direct.ca!look.ca!news.maxwell.syr.edu!news-was.dfn.de!news-koe1.dfn.de!RRZ.Uni-Koeln.DE!nntp.CS.Uni-Magdeburg.De!PeerFeed.KWeb.on.ca!dnews