How to create a PivotTable in Transact/SQL?

Question

My source data table is

MemID Condition_ID Condtion_Result
----------------------------------
1     C1           0
1     C2           0
1     C3           0
         


        

Answer 1

You need to use a PIVOT. You can use either a STATIC PIVOT where you know the values of the columns to transform or a DYNAMIC PIVOT where the columns are unknown until execution time.

Static Pivot (See SQL Fiddle with Demo):

select *
from 
(
    select memid, Condition_id, Condition_Result
    from t
) x
pivot
(
    sum(condition_result)
    for condition_id in ([C1], [C2], [C3], [C4])
) p

Dynamic Pivot (See SQL Fiddle with Demo):

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

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.condition_id) 
            FROM t c
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')


set @query = 'SELECT memid, ' + @cols + ' from 
            (
                select MemId, Condition_id, condition_result
                from t
           ) x
            pivot 
            (
                sum(condition_result)
                for condition_id in (' + @cols + ')
            ) p '


execute(@query)

Both will generate the same results.