如何在第三個變量mysql查詢中求和兩個子查詢的總和？

Question

我正在嘗試匯總喜歡和評論的總數，但結果始終為零（0），因為我已經實施了大部分發現但沒有成功的解決方案，請幫助我解決此問題。

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

您不能在定義它們的同一SELECT中使用列別名。 我建議在FROM子句中這樣做：

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。 如果是這樣，則應刪除SELECT DISTINCT 。 它只會對性能產生不利影響。

Answer 2

你可以這樣嘗試

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