MySQL Workbench 最大计数

Question

作为一个 SQL 傻瓜，我对尝试最多 2 列计数感到非常困惑。

我有一个交易数据库，我想为每个用户获取频率最高的收件人。

数据是:

User  Recipient 
 A        B
 A        C
 A        B
 A        F
 D        A
 D        C
 D        A
 D        A

想要的结果是

User Recipient Count
 A      B       2
 D      A       3

我设法得到计数，但我似乎无法得到最大接收者。

我试过使用内部联接和 where 语句，但都失败了。

在平局的情况下，显示哪个值并不重要。

Answer 1

在 MySQL 中获得最大值有点痛苦。这是一种方法:

select user, recipient, count(*)
from t
group by user, recipient
having count(*) = (select count(*)
                   from t t2
                   where t2.user = t.user
                   group by user, recipient
                   order by count(*) desc
                   limit 1
                  );

注意:此版本将在有平局时返回重复项。如果您不想重复，您可以这样做:

select user, recipient, count(*)
from t
group by user, recipient
having recipient = (select recipient
                    from t t2
                    where t2.user = t.user
                    group by user, recipient
                    order by count(*) desc
                    limit 1
                   );