As an example

select 'Count IsPrimary', [0], [1]

from (select isprimary, blockid from block) b

pivot (

count(blockid)

for isprimary in ([0],[1])

) pWill work

Based on a quick glance at you procedure I'm guessing you producing something like

select 'Count IsPrimary',, [0], [1]

from (select isprimary, blockid from block) b

pivot (

count(blockid)

for isprimary in (,[0],[1])

) pWhich will generate a syntax error.

If you trim the leading comma off the columns you query should start working. But that is a guess as I can't test it. You may want to change exec(@query) to select @query and post the actual query that is being generated.