# PRIMARY key not working
**URL:** https://forums.percona.com/t/primary-key-not-working/983
**Category:** Other MySQL® Questions
**Created:** [October 29, 2008, 10:59am UTC](https://forums.percona.com/t/primary-key-not-working/983 "2008-10-29T10:59:55Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@jeffStrahl](https://forums.percona.com/u/jeffStrahl)
#### Post date: [October 29, 2008, 10:59am UTC](https://forums.percona.com/t/primary-key-not-working/983/1 "2008-10-29T10:59:55Z")
Hello,
I have a query that is joining multiple tables. I have it optimized rather well, except for one table. I can’t for the life of me figure out why that table is not using the pk as the key. It is causing the query to filesort and use a temp table, changing the query time from 0.003s to 23s, obviously too long.
Attached is a file with the database and query details.
Any assistance is greatly appreciated, for I don’t know what it could be.
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### Author:  [@xaprb](https://forums.percona.com/u/xaprb)
#### Post date: [December 25, 2009, 10:36am UTC](https://forums.percona.com/t/primary-key-not-working/983/2 "2009-12-25T10:36:32Z")
I can’t see what could be causing that, either. Maybe ANALYZE TABLE method\_of\_payment will help.
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### Author:  [@gmouse](https://forums.percona.com/u/gmouse)
#### Post date: [December 27, 2009, 7:12pm UTC](https://forums.percona.com/t/primary-key-not-working/983/3 "2009-12-27T19:12:16Z")
actually I have encountered that old versions of MySQL (5.0.x, have not tried anything more recent) has a hard job selecting the right index for order by. Eg having a multicolumn indices on (a,b) and on (a,c), if you select from tbl where a=1 order by c it would still pick the index on (a,b). Only using force index solves this issue (or adding an arbitrary where-clause like c\>0).