SQL: Merge Date Ranges

Question

I\'ve a table, which describes work slices of a business working calendar: (date format is 24 hours format)

PK  | STARTDATE          | ENDDATE
______________         


        

Answer 1

This is my solution.

IF OBJECT_ID('tempdb..#tblDates') IS NOT NULL
    DROP TABLE #tblDates

CREATE TABLE #tblDates (AutoId INT IDENTITY, StartDate DATE, EndDate DATE)

INSERT #tblDates (StartDate, EndDate) SELECT '2014-11-02', '2014-11-08'
INSERT #tblDates (StartDate, EndDate) SELECT '2014-11-07', '2014-11-10'
INSERT #tblDates (StartDate, EndDate) SELECT '2014-11-06', '2014-11-12'

INSERT #tblDates (StartDate, EndDate) SELECT '2014-11-02', '2014-11-15'

INSERT #tblDates (StartDate, EndDate) SELECT '2014-12-10', '2014-12-13'
INSERT #tblDates (StartDate, EndDate) SELECT '2014-12-12', '2014-12-15'
INSERT #tblDates (StartDate, EndDate) SELECT '2014-12-14', '2014-12-16'


-- Optional / Remove the duplicated records of same StartDate and EndDate
DELETE FROM #tblDates WHERE AutoId NOT IN (SELECT MAX(AutoId) FROM #tblDates GROUP BY StartDate, EndDate)

-- Optional / Get only the record with max EndDate grouped by StartDate, Remove Others
DELETE  d1
FROM    #tblDates d1
        JOIN (SELECT x.StartDate, MAX(x.EndDate) MAXEndDate FROM #tblDates x GROUP BY x.StartDate) d2 ON d2.StartDate = d1.StartDate AND d2.MAXEndDate != d1.EndDate

-- Optional / Get only the record with min StartDate grouped by EndDate, Remove Others
DELETE  d1
FROM    #tblDates d1
        JOIN (SELECT x.EndDate, MIN(x.StartDate) MINStartDate FROM #tblDates x GROUP BY x.EndDate) d2 ON d2.EndDate = d1.EndDate AND d2.MINStartDate != d1.StartDate

-- Optional / Remove the overlapping ranges of relevant StartDate and EndDate
DELETE  c
FROM    #tblDates p
        JOIN #tblDates c ON c.AutoId != p.AutoId AND c.StartDate BETWEEN p.StartDate AND p.EndDate AND c.EndDate BETWEEN p.StartDate AND p.EndDate


;WITH Ranges
AS
(
    SELECT  s.StartDate, s.EndDate
    FROM    #tblDates s
            LEFT JOIN #tblDates a ON a.AutoId != s.AutoId AND s.StartDate BETWEEN a.StartDate AND a.EndDate AND s.StartDate != a.StartDate
    WHERE   a.AutoId IS NULL
    UNION ALL
    SELECT  r.StartDate, d.EndDate
    FROM    Ranges r
            JOIN #tblDates d ON r.EndDate != d.EndDate AND r.EndDate BETWEEN d.StartDate AND d.EndDate
)

SELECT StartDate, MAX(EndDate) EndDate FROM Ranges GROUP BY StartDate