Question

我有以下表格......

任务 alt text http://img260.imageshack.us/img260/3695/screenshotbg.png

人 alt text http://img685.imageshack.us/img685/6445/screenshot1f.png

tasks_people alt text http://img260.imageshack.us/img260/1061/screenshot2r.png

...我希望获得一份任务列表，并分配给他们的人数。请注意，可以多次将人员分配到任务（在不同日期）。出于某种原因，我似乎无法管理它。

感谢您的帮助！

Answer 1

如果你想让同一个人的许多作业被算作1做：

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

否则只需count()

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

Answer 2

我无法看到您的表格结构，但您可以尝试从tasks_people（distinct taskid，personid）中选择不同的值，然后进行计数和分组。

Answer 3

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

如果计数+明显不正常（即花费太长时间），你可以试试这个：

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

mysql分配给任务的人数

3 个答案: