Why can't I use an alias for an aggregate in a having clause?

Question

My code is like shown below :

select col1,count(col2) as col7
from --some join operation
group by col1
having col7 >= 3 -- replace col7 by count(col2) to          


        

Answer 1

You should select twice to use the count() column

select * from (select col1,count(col2) as col7
from --some join operation
group by col1) as temp
where temp.col7 >= 3