MySQL variable/alias not usable

So what I'm trying to do at the moment is to select a dataset of values depending on another autocalculated v开发者_运维百科alue.(Sounds pretty complicated. It isn't I think and I'm not that much into english)

My SQL code looks like this:

SELECT ticket.ref_id AS id, COUNT( * ) AS reports, (COUNT(*)/post.views) AS
treshold,post.views AS views
FROM ticket, post
WHERE ticket.ref_id = post.id AND (reports/post.views)
GROUP BY ref_id
ORDER BY views,reports DESC

The problem is, when I try to use treshold or reports in the WHERE clause the query fails and says that there is no such value in 'field list'. I know where the problem is, it's that MySQL seems not to allow the use of 'self defined' fields in the WHERE clause but i really need this and I dont know how to fix it.

Just using COUNT(*) doesn't work either because it doesn't know what to count.

Can anyone help me on this problem? I think it's totally basic SQL but I'm stuck on this at the moment.

You can use the the HAVING clause instead of WHERE for the unreferencable columns. It's less performant, but it will do the job.

http://dev.mysql.com/doc/refman/5.0/en/select.html

The HAVING clause is applied nearly last, just before items are sent to the client, with no optimization. (LIMIT is applied after HAVING.)

A HAVING clause can refer to any column or alias named in a select_expr in the SELECT list or in outer subqueries, and to aggregate functions