如何使用三个表编写这个复杂的MySQL查询？

Question

我有以下三个表：

1. 任务表-task_id，activity_id（FOREIGN KEY），开始日期，结束日期

2. 活动表-activity_id，Milestone_id（FOREIGN KEY），other_fields

3. 里程碑表-milestone_id，project_id，other_fields

现在我想要这样的结果集

No_of_task(count) | no_activity | milestone_name
      5           :     2       :    ABC Milestone

我想计算end_dated任务，根据end_date任务和里程碑名称计算活动。

例如，具有5个活动和20个不同任务的1个里程碑名称Housing_Construction ... end_dated一些任务

像这样的housing_construction 3活动的5个任务结束。

任务表说明

+-----------------------+-------------+------+-----+---------+----------------+
| Field                 | Type        | Null | Key | Default | Extra          |
+-----------------------+-------------+------+-----+---------+----------------+
| activity_task_id      | int(11)     | NO   | PRI | NULL    | auto_increment |
+-----------------------+-------------+------+-----+---------+----------------+
| milestone_activity_id | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| task                  | varchar(50) | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| description           | text        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| assign_to_employee_id | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| assign_date           | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| task_end_date         | date        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| tasktime              | varchar(50) | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| status                | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| is_delete             | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| entry_employee_id     | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| edit_employee_id      | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| createddatetime       | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| modifydatetime        | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| nooftimesedit         | smallint(6) | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| completion_date       | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+

活动表说明

+-----------------------+-------------+------+-----+---------+----------------+
| Field                 | Type        | Null | Key | Default | Extra          |
+-----------------------+-------------+------+-----+---------+----------------+
| milestone_activity_id | int(11)     | NO   | PRI | NULL    | auto_increment |
+-----------------------+-------------+------+-----+---------+----------------+
| project_milestone_id  | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| activityname          | varchar(50) | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| activity_end_date     | date        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| activity_description  | text        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| status                | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| is_delete             | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| entry_employee_id     | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| edit_employee_id      | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| createddatetime       | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| modifydatetime        | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| nooftimesedit         | smallint(6) | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+

里程碑表说明

+-----------------------+-------------+------+-----+---------+----------------+
| Field                 | Type        | Null | Key | Default | Extra          |
+-----------------------+-------------+------+-----+---------+----------------+
| project_milestone_id  | int(11)     | NO   | PRI | NULL    | auto_increment |
+-----------------------+-------------+------+-----+---------+----------------+
| project_id            | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| milestone             | varchar(50) | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| milestone_description | text        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| milestone_end_date    | date        | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| status                | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| is_delete             | tinyint(1)  | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| entry_employee_id     | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| edit_employee_id      | int(11)     | YES  | MUL | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| createddatetime       | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| modifydatetime        | datetime    | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+
| nooftimesedit         | smallint(6) | YES  |     | 0       |                |
+-----------------------+-------------+------+-----+---------+----------------+
| noofdays              | int(11)     | YES  |     | NULL    |                |
+-----------------------+-------------+------+-----+---------+----------------+

Answer 1

尝试这个：

select 
    count(distinct t.activity_task_id) No_of_task,
    count(distinct a.milestone_activity_id) no_activity,
    m.milestone_description milestone_name
from milestone m
inner join activity a
    on m.project_milestone_id = a.project_milestone_id
inner join task t
    on a.milestone_activity_id = t.milestone_activity_id
where t.status != 4
and t.task_end_date < curdate()
group by m.project_milestone_id,
    m.milestone_description;

Answer 2

您可以为此目的使用JOIN ，请使用以下代码，

SELECT COUNT(T.task_id) as no_of_task,
       COUNT(A.activity_id) as no_of_activity,
       MAX(M.milestone_name)  as milestone_name
FROM milestone M 
INNER JOIN activity A on M.milestone_id=A.milestone_id
INNER JOIN task T on T.activity_id =A.activity_id 
GROUP BY A.activity_id,T.task_id
HAVING T.end_date < curdate()