Hi all, I can see a cartesian product on the EMP table. Is this really what you're looking for. There is no column joining T2 and T3 !
Also as Peter said, you should have a lack of indexes on your tables. If you can send me your .frm,.myd and .myi files of the two tables as a zip file, I may help you to execute your query in less than 20mn. Question : count(*) from EMP = ? Mathias -----Original Message----- From: Peter Brawley [mailto:[EMAIL PROTECTED] Sent: dimanche 24 avril 2005 17:39 To: [EMAIL PROTECTED] Cc: mysql@lists.mysql.com Subject: Re: mysql_performance Moemen, You assign a string _position_ result from LOCATE to a SUBSTRNG _length_ argument. Is that what you mean? Do you have indexes on persons.item_id, emp (item_id, item_type, f2, f6, f7)? Once there are such indexes, try ordering the WHERE ... ANDs to correspond to those keys so the optimiser can use the index If it takes 20 mins, you likely have lots of rows, and the per-row SUBSTRING(...LOCATE...) calls will likely slow it down. If the above changes don;t help, you could try breaking out the substrings to separate columns and index on them too. Try running EXPLAIN on your query before & after such changes to see if you're changing the query engine's plan. HTH Peter Brawley http://www.artfulsoftware.com ----- moemen saad eldeen wrote: >Dear all, > >I have a problem running this query > > >"select distinct T1.item_id, T1.f2 from Persons as T1 , Emp as >T2 , Emp as T3 where T1.item_type='6.' and T2.item_type='6.1.9.' >and >T3.item_type='6.1.' and T2.f2 like '1.1.16.%' and >substring(T2.item_id,1,LOCATE('.',T2.item_id))=T1.item_id and >substring(T3.item_id,1,LOCATE('.',T3.item_id))=T1.item_id and >(T3.f2 >='4.1.1.') and (T3.f7 is null ) and (T2.f6 is null ) order by >T1.f2 >" > > >on my server the output come after about 20 mins i have tried all >possible solutions for tunning my server using : > >1-server parameters like: increasing key_buffer,read buffer,setting >result buffer, disable swapping >2-high memory: 2GB RAM > > >All my tables are MYISAM and with varchar type > >I don't know how to speeding output > > >can anyone help > > > > > > > > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.10.2 - Release Date: 4/21/2005 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
