Question

我有一个节点喜欢的表，看起来大致如下：

lid nid uid type
1   23  3   like
2   23  1   like
3   49  3   dislike
4   11  6   like

lid =此表的唯一ID，nid =“node”（内容）ID，uid =用户ID和类型是不言自明的。

使用此查询：

SELECT nid, COUNT(lid) AS score, type
FROM node_likes
INNER JOIN users ON node_likes.uid = users.uid
GROUP BY nid, type

我可以让每个节点都有喜欢和不喜欢的分数。内连接是无关紧要的;一些（dis）喜欢来自不再存在的用户，并且联接是为了消除它们。

结果如下：

nid score type
307 4     like
307 1     dislike
404 24    like

如何按type对此查询进行子分组，并返回每个“喜欢”类型的最高得分节点ID（如/不喜欢）？

即

nid score type
404 24    like
307 1     dislike

Answer 1

SELECT
    SUBSTRING_INDEX(GROUP_CONCAT(nid ORDER BY likes DESC),',',1) as most_likes_nid,
    MAX(likes) as most_likes,
    SUBSTRING_INDEX(GROUP_CONCAT(nid ORDER BY dislikes DESC),',',1) as most_dislikes_nid,
    MAX(dislikes) as most_dislikes
FROM (
    SELECT 
        nid,
        COUNT(IF(type = 'like', 1, null)) as likes,
        COUNT(IF(type = 'dislike', 1 ,null)) as dislikes
    FROM node_likes
    GROUP BY nid 
) as t

Answer 2

    SELECT nid, COUNT(lid) AS score, type
    FROM node_likes
    INNER JOIN users ON node_likes.uid = users.uid
    GROUP BY nid, type        
    ORDER BY type DESC, score DESC;

可能会做到这一点。

Answer 3

试试这个：

SELECT 
    nid, max(score) as score, type
FROM (
    SELECT nid, COUNT(lid) AS score, type
    FROM node_likes
    INNER JOIN users ON node_likes.uid = users.uid
    GROUP BY nid, type
) results
GROUP BY type
ORDER BY type DESC, score DESC

按分组列分组？

3 个答案: