MySQL分配给任务的人数

如果您希望将同一个人的多个任务计数为1,请执行以下操作:

select tasks.task_id, tasks.title, count(distinct tasks_people.people_id) 
as p_counter
from tasks left join tasks_people
on tasks.task_id = tasks_people.task_id
group by tasks.task_id

否则很简单 count() 它

select tasks.task_id, tasks.title, count(tasks_people.people_id) as p_counter
from tasks left join tasks_people
on tasks.task_id = tasks_people.task_id
group by tasks.task_id

我看不到您的表结构,但是您可以尝试从任务人员(distinct taskid,personid)中选择不同的值,然后计数和分组。

select task_id, count(distinct people_id) as people_assigned_to_task
from tasks_people
group by task_id

如果计数+明显的错误行为(即花费太长时间),您可以尝试以下方法:

select task_id, 
(select count(*) from 
      (
          select distinct people_id from tasks_people i 
          where i.task_id = o.task_id
      ) 
) as people_assigned_to_task
from tasks_people o
group by task_id