Question

我有一个像（短）的用户表：

id (BIGINT)
username (VARCHAR)
recommendedByUserId (BIGINT)

在recommendedByUserId中存储推荐人的ID，即推荐人的users.id - 值。

现在我需要知道每个users.id在users.recommendedByUserId中的次数，并对它们进行降序排序，因此具有最多推荐的用户位于结果之上。

我试过了：

SELECT u.username, COUNT(r.id) FROM users u INNER JOIN users r ON u.id = r.recommendedByUserId

但这不起作用。

Answer 1

如果id足够

SELECT recommendedByUserId, COUNT(*) as rec_cnt
FROM users u 
group by recommendedByUserId
order by rec_cnt desc

如果您还需要该名称，则可以

select u.username, x.rec_cnt 
from users u
inner join
(
    SELECT recommendedByUserId as id, COUNT(*) as rec_cnt 
    FROM users u 
    group by recommendedByUserId
) x on x.id = u.id
order by x.rec_cnt desc

Answer 2

SELECT recommendedByUserId, COUNT(*) as cnt
FROM users us 
group by recommendedByUserId order by cnt desc;

MySQL连接在一个表上

2 个答案: