MySQL where 子句和 avg() 作为子查询的排序

MySQL where clause and ordering by avg() as a sub query(MySQL where 子句和 avg() 作为子查询的排序)

问题描述

虽然我可以对别名子查询进行分组和排序，但我不能在 where 子句中使用别名.我需要改用联接吗?

Although I can group and order by on an aliased sub query, I can't use the alias in a where clause. Do I need to use a join instead?

作品:

SELECT entries.*, 
    (SELECT avg(value) 
    FROM `ratings`
    WHERE ratings.entry_id = entries.id) as avg_rating
FROM `entries` 
ORDER BY avg_rating DESC

失败(where 子句中的未知列 'avg_rating'"):

Fails ("unknown column 'avg_rating' in where clause"):

SELECT entries.*, 
    (SELECT avg(value) 
    FROM `ratings` 
    WHERE ratings.entry_id = entries.id) as avg_rating 
FROM `entries` 
WHERE avg_rating < '4.5000' ORDER BY avg_rating DESC

推荐答案

您可以使用 HAVING 子句而不是 WHERE 来做到这一点

You may be able to do this with a HAVING clause instead of a WHERE

语法

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