Pivot with an indefinite amount of distinct values

Question

I have written this query:

SELECT s, [1] AS a1, [2] AS a2, [3] AS a3, [4] AS a4
FROM (SELECT grade, aid, s FROM m) p
PIVOT
(
SUM(grade)
FOR aid IN ([1], [2], [3]         


        

Answer 1

You will need to use a Dynamic Pivot to get the list of columns that you want. This will retrieve the list of columns first and then pivot that list. Something similar to this:

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX);

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(aid) 
            FROM m 
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT s, ' + @cols + ' from 
            (
                select grade, aid, s
                from m
           ) x
            pivot 
            (
                sum(grade)
                for aid in (' + @cols + ')
            ) p 
            ORDER BY p.s'

execute(@query)