Consolidating subsets in a table - sql

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

Answer 2

Also using a CTE, but in a slightly different way
DECLARE #Consolidate TABLE (
UserID INTEGER, StartWeek INTEGER,
EndWeek INTEGER, Type CHAR(1))
INSERT INTO #Consolidate VALUES (1, 1, 3, 'A')
INSERT INTO #Consolidate VALUES (1, 4, 5, 'A')
INSERT INTO #Consolidate VALUES (1, 6, 10, 'A')
INSERT INTO #Consolidate VALUES (1, 14, 16, 'A')
INSERT INTO #Consolidate VALUES (1, 11, 13, 'B')
INSERT INTO #Consolidate VALUES (2, 1, 5, 'A')
INSERT INTO #Consolidate VALUES (2, 6, 9, 'A')
INSERT INTO #Consolidate VALUES (2, 10, 16, 'B')
;WITH ConsolidateCTE AS
(
SELECT UserID, StartWeek, EndWeek, Type
FROM #Consolidate
UNION ALL
SELECT cte.UserID, cte.StartWeek, c.EndWeek, c.Type
FROM ConsolidateCTE cte
INNER JOIN #Consolidate c ON
c.UserID = cte.UserID
AND c.StartWeek = cte.EndWeek + 1
AND c.Type = cte.Type
)
SELECT UserID, [StartWeek] = MIN(Startweek), EndWeek, Type
FROM (
SELECT UserID, Startweek, [EndWeek] = MAX(EndWeek), Type
FROM ConsolidateCTE
GROUP BY UserID, StartWeek, Type
) c
GROUP BY UserID, EndWeek, Type
ORDER BY 1, 2, 3