Question

我的网络应用中有帖子，评论和喜欢。我想通过“得分”来订购帖子，这只是喜欢和评论的总和。

我正在尝试做这样的事情：

SELECT posts.id, COUNT(comments.id) AS c, COUNT(likes.id) AS l 
FROM posts 
LEFT JOIN comments ON posts.id = comments.post_id 
LEFT JOIN likes ON posts.id = likes.post_id 
GROUP BY posts.id 
ORDER BY SUM(c,l) desc;

但是我收到关于列c不存在的错误;

或者这个：

SELECT posts.id, sum(count(comments.id), count(likes.id)) AS score 
FROM posts
LEFT JOIN comments ON posts.id = comments.post_id 
LEFT JOIN likes ON posts.id = likes.post_id 
GROUP BY posts.id 
ORDER BY score desc;

但我收到有关名称和参数类型的错误。

是否有不同的方式来编写此查询以使其有效？谢谢！

Answer 1

你在大致正确的轨道上，但出于某种原因，你试图使用简单加法的sum聚合内容：

SELECT posts.id, count(comments.id) + count(likes.id) AS score 
FROM posts
LEFT JOIN comments ON posts.id = comments.post_id 
LEFT JOIN likes ON posts.id = likes.post_id 
GROUP BY posts.id 
ORDER BY 2 desc;

我在这里使用了序数位置排序顺序，即按第二列排序。

Postgresql顺序加入后的计数总和

1 个答案: