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mysql dont use my Index?
Posted by: Johannes Fosseus
Date: January 12, 2006 08:22AM


I do have this sql-question and when I run 'explain' on this i can see it uses all rows in the table, rows = 86771, and mysql tell me that there is a possible key, 'writerid' and that it uses NULL key. Not good for my perfonmance!

Well, the thing is that I have an index in the junior_text, writerid INDEX?

Anyone have a clue why mysql dont use that index?

table type possible_keys key key_len ref rows Extra
junior_text ALL writerid NULL NULL NULL 86771 Using where; Using temporary; Using filesort
junior_writer eq_ref PRIMARY PRIMARY 4 junior_text.writerid 1 Using where

my sql:
EXPLAIN SELECT junior_text.textid, junior_text.texthead, junior_text.textcreatedlong, junior_text.commentnbr, junior_writer.writerid, junior_writer.writername, junior_writer.status
FROM junior_text, junior_writer
WHERE junior_text.textactive =1
AND junior_text.writerid = junior_writer.writerid
AND DATE_FORMAT( junior_text.textcreatedlong, '%Y-%m-%d' ) = '2006-01-12'
AND junior_writer.hidden =0
AND junior_text.foldersid NOT IN ( 28 )
GROUP BY junior_text.textid
ORDER BY textcreatedlong DESC

regards Johannes.

Edited 4 time(s). Last edit at 01/12/2006 08:25AM by Johannes Fosseus.

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mysql dont use my Index?
January 12, 2006 08:22AM
January 18, 2006 10:36PM

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