Oracle-L: sql optimization question

From: Guang Mei <gmei_at_incyte.com>
Date: Wed, 27 Aug 2003 09:59:27 -0800
Message-ID: <F001.005CD822.20030827095927@fatcity.com>

Hi,

This query took a few minues to return 126K rows (fast):

select distinct n.cognateid, m.isirefid,4, linkdate from mt.externallink l, refidmatch m, nametag n where l.objectid = n.geneid
and m.pubmedid = l.identifier
and externaldbid = 9;

But this query took hours and still no result, I had to kill it:

select distinct n.cognateid, m.isirefid,4, linkdate from mt.externallink l, refidmatch m, nametag n where l.objectid = n.geneid
and m.pubmedid = l.identifier
and externaldbid = 9
and (select count(distinct objectid) from mt.externallink k

     where k.identifier = l.identifier
     and externaldbid = 9
     and l.objectid !=k.objectid)<5;

All the related columns are indexed and table are analyzed. Is there a way to re-write the part

select count(distinct objectid) from mt.externallink k

     where k.identifier = l.identifier
     and externaldbid = 9
     and l.objectid !=k.objectid)<5

to make the whole thing faster?

TIA. Guang

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Author: Guang Mei
INET: gmei_at_incyte.com

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