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POSQL Duplicate Delete Query over Millions of Rows for Performance
 

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    <p>This has been an adventure. I started with the looping duplicate query located in <a href="https://stackoverflow.com/questions/161960">my previous question</a>, but each loop would go over all <strong>17 million records</strong>, <strong>meaning it would take weeks</strong> (just running <code>*select count * from MyTable*</code> takes my server 4:30 minutes using MSSQL 2005). I gleamed information from this site and at this <a href="http://weblogs.sqlteam.com/jeffs/archive/2007/03/28/60146.aspx" rel="nofollow noreferrer">post</a>.</p> <p>And have arrived at the query below. The question is, is this the correct type of query to run on 17 million records for any type of performance? If it isn't, what is?</p> <p>SQL QUERY:</p> <pre><code>DELETE tl_acxiomimport.dbo.tblacxiomlistings WHERE RecordID in (SELECT RecordID FROM tl_acxiomimport.dbo.tblacxiomlistings EXCEPT SELECT RecordID FROM ( SELECT RecordID, Rank() over (Partition BY BusinessName, latitude, longitude, Phone ORDER BY webaddress DESC, caption1 DESC, caption2 DESC ) AS Rank FROM tl_acxiomimport.dbo.tblacxiomlistings ) al WHERE Rank = 1) </code></pre>
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