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POT SQL - Eloquent replacement of Correlated Subquery
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copied!<p>I have a query that is currently using a correlated subquery to return the results, but I am thinking the problem could be solved more eloquently perhaps using ROW_NUMBER().</p> <p>The problem is around the profile of a value v, through a number of years for an Item. Each item has a number of versions, each with its own profile whick starts when the version is introduced and the data currently looks like this:</p> <pre> ItemId ItemVersionId Year Value =========================================== 1 1 01 0.1 1 1 02 0.1 1 1 03 0.2 1 1 04 0.2 1 1 05 0.2 1 1 06 0.3 1 1 07 0.3 1 1 08 0.4 1 2 04 0.3 1 2 05 0.3 1 2 06 0.3 1 2 07 0.4 1 2 08 0.5 1 3 07 0.6 1 3 08 0.7 2 1 01 0.1 2 1 01 0.1 2 1 01 0.2 etc </pre> <p>I want to return the full profile for an Item using the most recent version where applicable. For the above example for item 1:</p> <pre> ItemId ItemVersionId Year Value =========================================== 1 1 01 0.1 1 1 02 0.1 1 1 03 0.2 1 2 04 0.3 1 2 05 0.3 1 2 06 0.3 1 3 07 0.6 1 3 08 0.7 </pre> <p>I am currently using</p> <pre><code>SELECT ItemId, ItemVersionId, Year, Value FROM table t WHERE ItemId = 1 AND ItemVersionId = (SELECT MAX(ItemVersionId) FROM table WHERE ItemId = t.ItemId AND Year = t.Year) </code></pre> <p>Whilst this returns the correct I suspect there is a more efficient way to do it, especially when the table gets large.</p> <p>I am using SQL Server 2005.</p> <p>Thanks in advance</p>

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