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    <p>Another possible way of doing this is</p> <pre><code>; --Ensure that any immediately preceding statement is terminated with a semicolon above WITH cte AS (SELECT ROW_NUMBER() OVER (PARTITION BY Col1, Col2, Col3 ORDER BY ( SELECT 0)) RN FROM #MyTable) DELETE FROM cte WHERE RN &gt; 1; </code></pre> <p>I am using <code>ORDER BY (SELECT 0)</code> above as it is arbitrary which row to preserve in the event of a tie. </p> <p>To preserve the latest one in <code>RowID</code> order for example you could use <code>ORDER BY RowID DESC</code> </p> <p><strong>Execution Plans</strong></p> <p>The execution plan for this is often simpler and more efficient than that in the accepted answer as it does not require the self join.</p> <p><a href="https://i.stack.imgur.com/ZJiWF.jpg"><img src="https://i.stack.imgur.com/ZJiWF.jpg" alt="Execution Plans"></a></p> <p>This is not always the case however. One place where the <code>GROUP BY</code> solution might be preferred is situations where a <a href="http://blogs.msdn.com/b/craigfr/archive/2006/09/20/hash-aggregate.aspx">hash aggregate</a> would be chosen in preference to a stream aggregate. </p> <p>The <code>ROW_NUMBER</code> solution will always give pretty much the same plan whereas the <code>GROUP BY</code> strategy is more flexible.</p> <p><a href="https://i.stack.imgur.com/iUlWm.jpg"><img src="https://i.stack.imgur.com/iUlWm.jpg" alt="Execution Plans"></a></p> <p>Factors which might favour the hash aggregate approach would be </p> <ul> <li>No useful index on the partitioning columns</li> <li>relatively fewer groups with relatively more duplicates in each group </li> </ul> <p>In extreme versions of this second case (if there are very few groups with many duplicates in each) one could also consider simply inserting the rows to keep into a new table then <code>TRUNCATE</code>-ing the original and copying them back to minimise logging compared to deleting a very high proportion of the rows.</p>
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    1. POHow can I remove duplicate rows?
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    1. USMartin Smith
    1. USMartin Smith
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    1. COIf I may add: The accepted answer doesn't work with tables that uses `uniqueidentifier`. This one is much simpler and works perfectly on any table. Thanks Martin.
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      1. USBrunoLM
    2. COThis is the only solution that is workable on my large table (30M rows). Wish I could give it more than +1
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      1. USJulia Hayward
    3. COThis is such an awesome answer! It worked event when I had removed the old PK before I realised there where duplicates. +100
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      1. USMikael Eliasson
 

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