Postgresql在連接後按順序計數

Question

我有我的webapp中的文章，評論和贊。我想用「分數」來排序，這只是喜歡和評論的總和。

我試圖做這樣的事情：

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; 

，但我得到C列不存在錯誤;

或者這樣：

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; 

，但我得到的名稱和參數類型的錯誤。

有沒有寫這個查詢，使得它的作品以不同的方式？謝謝！

Answer 1

你是在大致正確的軌道，但由於某些原因，你試圖用簡單的加法的sum骨料這一翻譯：

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; 

我這裏使用的序位排序順序，即爲了通過第2列。