mysql Count与 mysql中join 学习

** 期望：现在想统计 一个队伍下，所有人和所有人的总时长。**

原来写的是这样

修改为 这样就可以了

SELECT ref.team_id,
       count(distinct ref.account_id)        AS volunteerNum,
      sum(time.volunteer_duration) AS volunteerTimeTotal
      FROM volunteer_team_ref AS ref
         LEFT JOIN volunteer_duration AS time ON ref.account_id = time.account_id
where ref.is_deleted = '0'
GROUP BY ref.team_id;