计算给定值的行外观

Question

我有一个名为private_message的表格，其中包含以下字段：sender和receiver

我想知道特定发件人有多少次向某个人发送邮件，例如：

**Name**     **Times**
David        5
Michael      2
John         1

Answer 1

试试这个：

SELECT 
  sender as 'From',
  receiver as 'To',
  count(receiver) as 'Times'
FROM private_message
GROUP BY sender, receiver

结果可能类似于：

From         To         Times
David        Emil           5
Michael      Møller         2
John         Ringgaard      1
Emil         Ravinder       1