Question

given this table and data:

DECLARE @Table table (RowID int, RowCode char(1), RowValue int);set nocount on
INSERT @Table VALUES ( 6,'A',3757 )
INSERT @Table VALUES ( 5,'A',37827)
INSERT @Table VALUES (14,'A',48411)
INSERT @Table VALUES ( 1,'A',48386)
INSERT @Table VALUES (20,'A',48450)
INSERT @Table VALUES ( 7,'A',46155)
INSERT @Table VALUES (13,'A',721  )
INSERT @Table VALUES ( 2,'A',49335)
INSERT @Table VALUES (15,'A',4700 )
INSERT @Table VALUES (19,'A',64416)
INSERT @Table VALUES ( 8,'A',27246)
INSERT @Table VALUES (12,'B',54929)
INSERT @Table VALUES (16,'B',3872 )
INSERT @Table VALUES ( 3,'C',728  )
INSERT @Table VALUES (11,'C',1050 )
INSERT @Table VALUES ( 9,'C',3191 )
INSERT @Table VALUES (17,'C',866  )
INSERT @Table VALUES ( 4,'C',838  )
INSERT @Table VALUES (10,'D',550  )
INSERT @Table VALUES (18,'D',1434 );set nocount off

I need this:

                       VVVVVVVV
RowID RowCode RowValue RowChunk
----- ------- -------- --------
1     A       48386    1       
2     A       49335    1       
5     A       37827    1       
6     A       3757     1       
7     A       46155    1       
8     A       27246    2       
13    A       721      2       
14    A       48411    2       
15    A       4700     2       
19    A       64416    2       
20    A       48450    3       
12    B       54929    4       
16    B       3872     4       
3     C       728      5       
4     C       838      5       
9     C       3191     5       
11    C       1050     5       
17    C       866      5       
10    D       550      6       
18    D       1434     6    

RowChunk starts at 1 and is incremented by 1 for each RowCode change and/or when there have been 5 of the same RowCode values.

Answer 1

Basically my solution uses the same approach as yours, only with slightly different devices employed.

WITH NumberedRows AS (
  SELECT
    RowID,
    RowCode,
    RowValue,
    CodeChunk = (ROW_NUMBER() OVER (PARTITION BY RowCode ORDER BY RowID) - 1) / 5
  FROM @Table
)
SELECT
  RowID,
  RowCode,
  RowValue,
  RowChunk = DENSE_RANK() OVER (ORDER BY RowCode, CodeChunk)
FROM NumberedRows