Question

I have a table in SqlServer 2008 with data of the form

UserID  StartWeek  EndWeek   Type
1       1          3         A
1       4          5         A
1       6          10        A
1       11         13        B
1       14         16        A
2       1          5         A
2       6          9         A
2       10         16        B

I’d like to consolidate/condense the adjacent types so that the resulting table looks like this.

UserID  StartWeek  EndWeek   Type
1       1          10        A
1       11         13        B
1       14         16        A
2       1          9         A
2       10         16        B

Does anyone have any suggestions as to the best way to accomplish this? I’ve been looking at using Row_number and Partition, but I can’t get it to behave exactly as I’d like.

Answer 1

There’s probably a neater way to do it, but this produces the correct result

DECLARE @t TABLE
(UserId TINYINT
,StartWeek TINYINT
,EndWeek TINYINT
,TYPE CHAR(1)
)

INSERT @t
      SELECT 1,1,3,'A'
UNION SELECT 1,4,5,'A'
UNION SELECT 1,6,10,'A'
UNION SELECT 1,11,13,'B'
UNION SELECT 1,14,16,'A'
UNION SELECT 2,1,5,'A'
UNION SELECT 2,6,9,'A'
UNION SELECT 2,10,16,'B'

;WITH srcCTE
AS
(
        SELECT *
               ,ROW_NUMBER() OVER (PARTITION BY t1.UserID, t1.Type
                                   ORDER BY t1.EndWeek
                                   ) AS rn 
        FROM @t AS t1
)
,recCTE
AS
(
        SELECT *
               ,0 AS grp
        FROM srcCTE
        WHERE rn = 1

        UNION ALL

        SELECT s.UserId
               ,s.StartWeek
               ,s.EndWeek 
               ,s.TYPE 
               ,s.rn
               ,CASE WHEN s.StartWeek - 1 = r.EndWeek
                     THEN r.grp 
                     ELSE r.grp+ 1
                END AS GRP
        FROM srcCTE AS s
        JOIN recCTE AS r
        ON   r.UserId = s.UserId
        AND  r.TYPE   = s.TYPE
        AND  r.rn     = s.rn - 1
)
SELECT UserId
       ,MIN(StartWeek) AS StartWeek
       ,MAX(EndWeek)   AS EndWeek
       ,TYPE
FROM recCTE AS s1
GROUP BY UserId
         ,TYPE
         ,grp