Question

我有一个用户表，其中包含他们投票的用户ID，如下所示：

uid | voted_for
 1  |   3
 2  |   3
 3  |   1

我的目标是根据有多少人投票支持uid订购uid。但我不知道该怎么做。

所以最终的结果是：

uid | Total_Votes
 3  |     2
 1  |     1
 2  |     0

希望您能帮助解释为此构建SQL的最佳方法。

Answer 1

也许这样的事情将有助于自己加入表格：

SELECT u.*, voted_for_cnt
FROM users u
   LEFT JOIN (
      SELECT voted_for, count(1) voted_for_cnt 
      FROM users
      GROUP BY voted_for
   ) t ON u.uid = t.voted_for
ORDER BY t.voted_for_cnt DESC

SQL Fiddle Demo

Answer 2

这个简单的查询将产生您请求的输出：

select voted_for as uid, count(*) as total_votes
from users
group by 1
order by 2 desc

如果您想要输出中有关每个用户的所有数据，请将用户加入自身：

select u.*, count(v.uid) as total_votes
from users u
left join users v on v.voted_for = u.uid
group by 1,2,3,4,5 -- put as many numbers here as there are columns in the users table
order by total_votes desc

如果没有人投票给用户，则第二个查询将total_votes得分为零。

或者，您只能选择所需的列：

select u.uid, u.name, count(v.uid) as total_votes
from users u
left join users v on v.voted_for = u.uid
group by 1,2
order by 3 desc

```

要仅返回获奖者，请执行以下操作：

select u.uid, u.name, count(*) as total_votes
from users u
left join users v on v.voted_for = u.uid
group by 1,2
having count(*) = (
    select max(c) from (
        select count(*) as c from users group by voted_for))
order by 3 desc

按总计数顺序选择行

2 个答案: