For example, using the answer for this question:
http://stackoverflow.com/questions/152024/how-to-select-all-users-who-made-more-than-10-submissions "How to select all users who made more than 10 submissions."
select userId
from submission
group by userId
having count(submissionGuid) > 10
Let's say now I want to know many rows this sql statement outputted. How scalable is the solution for counting the rows of counting the rows?