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POHow to check dates don't overlap in a table using TSQL
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copied!<p>I have a table with start and finish datetimes that I need to determine if any overlap and not quite sure the best way to go.</p> <p>Initially I was thinking of using a nested cursor as shown below which does work, however I'm checking the same records against each other twice and I'm sure it is not very efficient.</p> <p>eg: this table would result in an overlap.</p> <pre><code>id start end ------------------------------------------------------- 1 2009-10-22 10:19:00.000 2009-10-22 11:40:00.000 2 2009-10-22 10:31:00.000 2009-10-22 13:34:00.000 3 2009-10-22 16:31:00.000 2009-10-22 17:34:00.000 Declare @Start datetime, @End datetime, @OtherStart datetime, @OtherEnd datetime, @id int, @endCheck bit Set @endCheck = 0 DECLARE Cur1 CURSOR FOR select id, start, end from table1 OPEN Cur1 FETCH NEXT FROM Cur1 INTO @id, @Start, @End WHILE @@FETCH_STATUS = 0 AND @endCheck = 0 BEGIN -- Get a cursor on all the other records DECLARE Cur2 CURSOR FOR select start, end from table1 and id != @id AND start < @end OPEN Cur2 FETCH NEXT FROM Cur2 INTO @OtherStart, @OtherEnd WHILE @@FETCH_STATUS = 0 AND @endCheck = 0 BEGIN if ( @Start > @OtherStart AND @Start < @OtherEnd OR @End > @OtherStart AND @End < @OtherEnd ) or ( @OtherStart > @Start AND @OtherStart < @End OR @OtherEnd > @Start AND @OtherEnd < @End ) BEGIN SET @endCheck = 1 END FETCH NEXT FROM Cur2 INTO @OtherStart, @OtherEnd END CLOSE Cur2 DEALLOCATE Cur2 FETCH NEXT FROM Cur1 INTO @id, @Start, @End END CLOSE Cur1 DEALLOCATE Cur1 </code></pre>

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