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POIs it possible to do a GROUP BY in SQL Server 2000 that returns the whole row?
 

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  1. POIs it possible to do a GROUP BY in SQL Server 2000 that returns the whole row?
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    <p>I have an SQL Server 2000 database that contains a view that shows meter readings for supply points which has the following columns:</p> <pre><code>- rh_sp_number &lt;- the number of the supply point - rh_... &lt;- a bunch of other columns pertaining to that specific reading row - rh_end_date &lt;- a `DateTime`field that holds the date of the reading </code></pre> <p>Each SupplyPoint can have 0..N readings. I need to fetch the last submitted row for any given SupplyPoint. And I want to accomplish this with <b>one</b> query to the Database.</p> <p>I need to do something like this:</p> <pre><code>var q = db.READINGS_HISTORY.Where(rh =&gt; ids.Contains(rh.rh_sp_number)) .GroupBy(rh =&gt; rh.rh_sp_number, rh =&gt; rh, (key, values) =&gt; values.OrderByDescending(rh =&gt; rh.rh_end_date).FirstOrDefault()) .ToList(); </code></pre> <p>In human language I need to select the last row of each group and return that row. Running this query (or any other combination that I could think of) will result in this:</p> <blockquote> <p>The execution of this query requires the APPLY operator, which is not supported in versions of SQL Server earlier than SQL Server 2005.</p> </blockquote> <p>I need to accomplish this in SQL Server 2000.</p> <p>It does not have to be a 'Group By' expression; anything that will return a maximum row for a given key will do.</p> <p><b>My solution:</b></p> <p>Based on Aarons answer I ended up with this query that does what I need (with a caveat, but business rules remove it form the equation for me).</p> <p>The caveat: <b>if there are same dates for same SupplyPoints the sql server will decide which row to choose</b></p> <pre><code>var hists = db.READINGS_HISTORY.Where(rh =&gt; ids.Contains(rh.rh_sp_number)) .GroupBy(rh =&gt; rh.rh_sp_number, rh =&gt; rh, (key, values) =&gt; new { key, date = values.Max(rh =&gt; rh.rh_end_date) }) .Join(db.READINGS_HISTORY, g =&gt; new { sp = g.key, date = g.date }, rh2 =&gt; new { sp = rh2.rh_sp_number, date = rh2.rh_end_date }, (g, rh) =&gt; rh) .Select(rh =&gt; new LastReading { //omitted.. }).ToList(); </code></pre>
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    1. USjuhan_h
    1. USjuhan_h
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    1. COI can't really read the first block of code. Can you show the table structure, identify the key values, some sample data, and desired results?
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      1. POIs it possible to do a GROUP BY in SQL Server 2000 that returns the whole row?
      1. USAaron Bertrand
    2. COI added some more info.
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      1. POIs it possible to do a GROUP BY in SQL Server 2000 that returns the whole row?
      1. USjuhan_h
    3. COCan you have LINQ call a stored procedure instead of all that mumbo-jumbo? I'm sure there's a way to make LINQ formulate the query in my answer, but I suspect it will be a lot less work if you create a stored procedure with that code and call it. Or perhaps a view will be easier to reference from LINQ?
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      1. POIs it possible to do a GROUP BY in SQL Server 2000 that returns the whole row?
      1. USAaron Bertrand
 

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