SQL Dynamic Pivot – how to order columns

You need to fix this:

SELECT  @listCol = STUFF(( SELECT distinct  '], [' + [size]
                           FROM     #t
                         FOR
                           XML PATH('')
                         ), 1, 2, '') + ']'

To return the columns in the right order. You might have to do something like this instead of using DISTINCT:

SELECT [size]
FROM     #t
GROUP BY [size]
ORDER BY MIN(BucketNum)