mysql - 你能在 MySQL 中将一个别名除以另一个吗？

Question

我有一个多表查询，类似这个(简化版)

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

问题出在 ORDER BY 子句中。这会导致显示 MySQL 错误，如下所示:

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

Answer 1

您无法使用别名进行计算。一种方法是简单地创建另一个别名并按其排序。

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