> -----Original Message----- > From: Tim Jones [mailto:TJones@xxxxxxxxx] > Sent: Tuesday, May 23, 2006 12:11 AM > To: pgsql-performance@xxxxxxxxxxxxxx > Subject: [PERFORM] slow query using sub select > > Hi, > I am having a problem with a sub select query being kinda slow. The > query is as follows: > > select batterycode, batterydescription, observationdate from Battery t1 > where patientidentifier=611802158 and observationdate = (select > max(observationdate) from Battery t2 where t2.batterycode=t1.batterycode > and patientidentifier=611802158) order by batterydescription. How about changing it into a standard join: select t1.batterycode, t1.batterydescription, t2.observationdate from Battery t1, (Select batterycode ,max(observationdate) from Battery t2 where patientidentifier=611802158 group by batterycode) AS T2 where t1. batterycode = t2. batterycode Jonathan Blitz AnyKey Limited Israel -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.6.1/344 - Release Date: 05/19/2006
