title: SQL Number - Row_Number() - Allow Repeating Row Number
body: <p>I'm using SQL Server 2008.  I have this data returned in a query that looks pretty much like this ordered by Day and ManualOrder...</p>
  
  <pre><code>ID   Day  ManualOrder  Lat     Lon    
  1    Mon  0            36.55   36.55  
  5    Mon  1            55.55   54.44  
  3    Mon  2            44.33   44.30  
  10   Mon  3            36.55   36.55  
  11   Mon  4            36.55   36.55  
  6    Mon  5            20.22   22.11  
  9    Mon  6            55.55   54.44  
  10   Mon  7            88.99   11.22  
  77   Sun  0            23.33   11.11  
  77   Sun  1            23.33   11.11  
  </code></pre>
  
  <p>What I'm trying to do is get this data ordered by Day, then ManualOrder...but I'd like a row counter (let's call it MapPinNumber).  The catch is that I'd like this row counter to be repeated once it encounters the same Lat/Lon for the same day again.  Then it can continue on with the next row counter for the next row if it's a different lat/lon.  We MUST maintain Day, ManualOrder ordering in the final result. </p>
  
  <p>I'll be plotting these on a map, and this number should represent the pin number I'll be plotting in ManualOrder order.  This data represents a driver's route and he may go to the same lat/lon multiple times during the day in his schedule.  For example he drives to Walmart, then CVS, then back to Walmart again, then to Walgreens.  The MapPinNumber column I need should be 1, 2, 1, 3.  Since he goes to Walmart multiple times on Monday but it was the first place he drives too, it's always Pin #1 on the map.  </p>
  
  <p>Here's what I need my result to be for the MapPinNumber column I need to calculate.  I've tried everything I can think of with ROW_NUMBER and RANK, and going insane!  I'm trying to avoid using an ugly CURSOR.</p>
  
  <pre><code>ID   Day  ManualOrder  Lat     Lon     MapPinNumber
  1    Mon  0            36.55   36.55   1
  5    Mon  1            55.55   54.44   2
  3    Mon  2            44.33   44.30   3
  10   Mon  3            36.55   36.55   1
  11   Mon  4            36.55   36.55   1
  6    Mon  5            20.22   22.11   4
  9    Mon  6            55.55   54.44   2
  10   Mon  7            88.99   11.22   5
  77   Sun  0            23.33   11.11   1
  77   Sun  1            23.33   11.11   1
  </code></pre>