Crear un cursor con un query Dinamico

declare @str nvarchar(1000)

declare @cstr nvarchar(2000)

 declare @id varchar(200)

set @str=N' select a.idProducto from inv_MaestraDeInventario a ' 

set @cstr = 'DECLARE c1 CURSOR FOR ' + @str

exec sp_executesql @cstr 

open c1

FETCH NEXT

FROM c1 INTO @id

WHILE @@FETCH_STATUS = 0

BEGIN

print @id

FETCH NEXT

FROM c1 INTO @id

END

CLOSE c1

DEALLOCATE c1