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.

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.

eg: this table would result in an overlap.

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
    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