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POSelect rows where column value has changed
 

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    <p>Let's say I have the following table:</p> <pre><code>Value Time 0 15/06/2012 8:03:43 PM 1 15/06/2012 8:03:43 PM * 1 15/06/2012 8:03:48 PM 1 15/06/2012 8:03:53 PM 1 15/06/2012 8:03:58 PM 2 15/06/2012 8:04:03 PM * 2 15/06/2012 8:04:08 PM 3 15/06/2012 8:04:13 PM * 3 15/06/2012 8:04:18 PM 3 15/06/2012 8:04:23 PM 2 15/06/2012 8:04:28 PM * 2 15/06/2012 8:04:33 PM </code></pre> <p>How do I select the starred rows, that is, where <code>Value</code> has changed? Basically I'm trying to find the time when <code>Value</code> has changed so I can do other queries based on those time intervals. The solution shouldn't depend on knowing <code>Value</code> or <code>Time</code> in advance.</p> <p>It seems to me that this shouldn't be very hard (but it's hard enough for me apparently!).</p> <p>I'm currently using SQL Server 2008 although I have access to 2012 if the new window/analytic functions are helpful.</p> <p>I tried adapting the solutions here <a href="http://blog.sqlauthority.com/2011/11/24/sql-server-solution-to-puzzle-simulate-lead-and-lag-without-using-sql-server-2012-analytic-function/">http://blog.sqlauthority.com/2011/11/24/sql-server-solution-to-puzzle-simulate-lead-and-lag-without-using-sql-server-2012-analytic-function/</a> but my query didn't complete after an hour! I think the joins explode the row size to something unmanageable (or I screwed it up).</p> <p>I can solve this problem with C# code and multiple db calls, but it seems like something that could be done in a table-valued function or SP which would be much nicer.</p> <p>Also, a solution that only works with increasing <code>Value</code> is OK if that is easier.</p>
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