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From:Craig (OFT) Weston Date:August 2 2007 6:01pm
Subject:RE: [mysql] reverse join
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 Thanks for your help. 

________________________________

From: Peter Brawley [mailto:peter.brawley@stripped] 
Sent: Thursday, August 02, 2007 10:47 AM
To: Weston, Craig (OFT); mysql@stripped
Subject: Re: [mysql] reverse join

 

Craig



>How do I pull out all the non-duplicate records?

With an exclusion join. To find non-duplicates with respect to one
key...

SELECT keycandidate
FROM tbl t1
LEFT JOIN tbl t2 ON t1.keycandidate=t2.keycandidate
WHERE t2.keycandidate IS NULL;

To expand the comparison to multiple keys...

SELECT key1, key2, ...
FROM tbl t1
LEFT JOIN tbl t2 ON t1.key1=t2.key2 AND t1.key2=t2.key2 AND ...
WHERE t2.key1 IS NULL;

PB

Weston, Craig (OFT) wrote: 

Hi there, 
 
            I have a situation where I have duplicate data within
several tables, but they are all indexed in the same way.  How do I pull
out all the non-duplicate records?
 
 
 
 
 
Would I have to create a temporary table, add one data set, then add the
second where it doesn't equal the first, and then do the same with the
third? Or is there a cleaner way?
 
 
 
 
 
Thanks,
 
Craig
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Thread
[mysql] reverse joinCraig \(OFT\) Weston2 Aug
  • Re: [mysql] reverse joinPeter Brawley2 Aug
    • RE: [mysql] reverse joinOFT)2 Aug