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POQuery to return 1 row of each duplicate
 

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    <p>I am using MS SQL 2008R2. I am working with a partial data set (i.e. not all colunms) and have not been able to exclude duplicate rows. For example, here are the rows for a claim:</p> <pre><code>Claim Line Doctor Received Paid 02195111345 1 22924 1995-11-13 2001-10-02 02195111345 1 22924 1995-11-13 2001-10-02 02195111345 2 22924 1995-11-13 2001-10-02 02195111345 2 22924 1995-11-13 2001-10-02 02195111345 3 22924 1995-11-13 2001-10-02 02195111345 3 22924 1995-11-13 2001-10-02 02195111345 4 22924 1995-11-13 2001-10-02 02195111345 4 22924 1995-11-13 2001-10-02 02195111345 5 22924 1995-11-13 2001-10-02 02195111345 5 22924 1995-11-13 2001-10-02 </code></pre> <p>I want to select only 1 row for each Claim+Line. There are additional columns, but they contain the same information for each combination of Claim+Line. </p> <p>I can easily identify the rows with duplicates with a query such as:</p> <pre><code>SELECT [ClaimNum],[ClaimNum_Line] FROM [dbo].[DamagedClaims] GROUP BY [ClaimNum],[ClaimNum_Line] HAVING COUNT(*) &gt; 1 </code></pre> <p>Typically, I would create a derived table using this query and join it back to the table - with another coulmn such as MAX(Version) or such, but there are no such columns with which to differentiate the duplicates.</p> <p>I have considered </p> <pre><code>SELECT ClaimNum], Line, MAX(DOCTOR), MAX([Date Received]), MAX([Date Paid]) </code></pre> <p>but there are about 20 columns and 750 million rows and that seemed like a lot of overhead (I am very sympathetic to our SQL Servers!). Is there a better solution?</p> <p>Best, Scott</p>
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