Dovresti utilizzare ISNULL()
funzione. Vedi SQL Fiddle
SELECT 'lessonid response ->'
, isnull([0], 0) as [0]
, isnull([1], 0) as [1]
, isnull([2], 0) as [2]
, isnull([3], 0) as [3]
, isnull([4], 0) as [4]
FROM (
SELECT lessonid AS 'lessonid response ->'
,ISNULL(response,0) as response
,count(response) AS respcnt
FROM tblRChoices
GROUP BY lessonid
,response
) TableResponse
PIVOT(SUM(respcnt) FOR response IN (
[0]
,[1]
,[2]
,[3]
,[4]
)) ResponsePivot