Question

I have the following sample data:

Id     Name     Quantity
1      Red      1
2      Red      3
3      Blue     1
4      Red      1
5      Yellow   3

So for this example, there are a total of 5 Red, 1 Blue, and 3 Yellow. I am looking for a way to group them by Color, but with a maximum of 2 items per group (sorting is not important). Like so:

Name     QuantityInPackage
Red      2
Red      2
Red      1
Blue     1
Yellow   2
Yellow   1

Any suggestions on how to accomplish this using T-SQL on MS-SQL 2005?

Answer 1

I would define a table containing sequential numbers, say 1 to 1000 and join that table (unless your database supports generating these numbers in the query like Oracle using CONNECT BY):

Table num

n
1
2
3
...

I tried the following query using Oracle (should work with TSQL too):

With summed_colors As (
  Select name, Sum(quantity) quantity
  From colors
  Group By name
)
Select
  name,
  Case When n*2-1 = quantity Then 1 Else 2 End quantityInPackage
From summed_colors
Join nums On ( n*2-1 <= quantity )
Order By name, quantityInPackage Desc

and it returns

Blue   1
Red    2
Red    2
Red    1
Yellow 2
Yellow 1