Question

我想总计喜欢和评论，但结果总是为零（0）请帮我解决这个问题，因为我已经实现了大多数我找到的解决方案但没有成功。

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子句中执行此操作：

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;

据推测，u.id是独一无二的。如果是这样，您应该删除SELECT DISTINCT。它只会对性能产生负面影响。

Answer 2

您可以尝试这样

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

如何在第三个变量mysql查询中求和两个子查询？

2 个答案: