mysql - 计算给定值在行中出现的次数

Question

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

我想知道特定发件人已向特定人员发送消息多少次，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