Basic join query understanding

Posted by OM The Eternity on Stack Overflow See other posts from Stack Overflow or by OM The Eternity
Published on 2010-05-10T05:59:03Z Indexed on 2010/05/10 6:04 UTC
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mysql

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left-join

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join

I know this very silly, but can anybody help me in understanding what does this join query is doing in elabortive description?

SELECT j1.* FROM jos_audittrail j1 LEFT OUTER JOIN jos_audittrail j2  ON (j1.trackid = j2.trackid AND j1.field = j2.field 
  AND j1.changedone < j2.changedone)
 WHERE j1.operation = 'UPDATE'  AND j1.trackid=$t_ids[$n] AND j2.id IS NULL

I know its very silly, but i need to go ahead with my further need... Pls do help me...

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