mysql - mysql orderby 对查询的选择部分中的操作不起作用？

Question

我设法编写了下面的查询，它几乎可以工作，问题是任何空值都被IFNULL(likes.num, 0)结果表末尾的 get 清零。

SELECT t.*, IFNULL(likes.num, 0)
FROM `textagname` as t
LEFT JOIN likes
ON t.tex = likes.tex
ORDER BY num DESC

有没有另一种方法来编写这个查询，而不是这样：

SELECT *
FROM (
    SELECT t.*, IFNULL(likes.num, 0)
    FROM `textagname` as t
    LEFT JOIN likes
    ON t.tex = likes.tex
)
ORDER BY d.num DESC

最好是一种不会使其花费更长的时间的方法。

score 1 · Accepted Answer

诀窍是按生成的值而不是来自表的值进行排序。请注意下面添加了 numLikes。

SELECT t.*, IFNULL(likes.num, 0) as numLikes
FROM `textagname` as t
LEFT JOIN likes
ON t.tex = likes.tex
ORDER BY numLikes DESC

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