Question

I have a multi-table query, similar to this (simplified version)

SELECT columns, count(table2.rev_id) As rev_count, sum(table2.rev_rating) As sum_rev_rating  FROM table1 LEFT JOIN table2 ON table1.dom_id = table2.rev_domain_from  WHERE dom_lastreview != 0 AND rev_status = 1  GROUP BY dom_url  ORDER BY sum_rev_rating/rev_count DESC 

The problem is in the ORDER BY clause. This causes a MySQL error to show, which is as follows:

Reference ‘sum_ rev_ rating’ not supported (reference to group function)

Answer 1

You’re not able to do calculations with aliases. One way of doing this would be to simply create another alias and order by that.

SELECT columns, count(table2.rev_id) As rev_count, sum(table2.rev_rating) As sum_rev_rating, sum(table2.rev_rating)/count(table2.rev_id) as avg_rev_rating FROM table1 LEFT JOIN table2 ON table1.dom_id = table2.rev_domain_from  WHERE dom_lastreview != 0 AND rev_status = 1  GROUP BY dom_url  ORDER BY avg_rev_rating DESC