Question

我有以下问题。似乎是一个简单的查询，但在花了这么多时间之后我无法弄明白。

Table
-----
project
mission
craft

项目可以有很多任务，对于每个任务，它可以使用多个航空工艺品。我想确定所有任务涉及的工艺品。

例如，如果有10个任务，任务1可以使用第1和第2工具。如果有任何工艺用于所有10个任务（任务1 -10），则应该输出。

我写道，

select craft,count(mission) from table group by craft

在此之后，我不知道如何将此值与总任务相匹配。任何帮助都将受到高度赞赏。

Answer 1

如果您需要单个项目，则需要根据任务总数来确定飞行任务的过滤器数量：

select c.id from (
   select c.id, count(mission_id) cnt
   from craft c inner join mission m on (m.id = c.mission_id)
   where m.project_id = <project_id> 
   group by c.id
) as c 
where c.cnt = (select count(*) from mission where project_id = <project_id>)

如果所有项目都需要这个：

select c.project_id, c.id from (
   select m.project_id, c.id, count(mission_id) cnt
   from craft c inner join mission m on (m.id = c.mission_id) 
   group by m.project_id, c.id
) as c inner join (
   select project_id, count(*) cnt
   from mission
   group by project_id
) as m on (m.project_id = c.project_id)
where c.cnt = m.cnt

Answer 2

with mission as (
    select distinct mission
    from craft
), craft_missions as (
    select craft, count(*) as total_missions
    from
        craft c
        inner join
        mission m on m.mission = c.mission
    group by craft
)
select craft
from craft_missions
where total_missions = (select count(*) from mission)

将总数与总数相匹配的好方法是什么？

2 个答案: