如何在第三个变量mysql查询中求和两个子查询的总和？

Question

我正在尝试汇总喜欢和评论的总数，但结果始终为零（0），因为我已经实施了大部分发现但没有成功的解决方案，请帮助我解决此问题。

SELECT DISTINCT id,name,picture,
(SELECT COUNT(id) from likes) as likes,
(SELECT COUNT(id) from comments) as comments,
(likes+comments) as total
From users

Answer 1

您不能在定义它们的同一SELECT中使用列别名。 我建议在FROM子句中这样做：

SELECT DISTINCT u.id, u.name, u.picture, l.likes, c.comments,
       (l.likes + c.comments) as total
FROM users u CROSS JOIN
     (SELECT COUNT(id) as likes FROM likes) l CROSS JOIN
     (SELECT COUNT(id) as comments FROM comments) c;

大概u.id是唯一的。 如果是这样，则应删除SELECT DISTINCT 。 它只会对性能产生不利影响。

Answer 2

你可以这样尝试

SELECT DISTINCT id,name,picture,
(SELECT COUNT(id) from likes) as likes,
(SELECT COUNT(id) from comments) as comments,
(SELECT COUNT(id) from likes)+(SELECT COUNT(id) from comments) as total
From users