Question

我有三张桌子：

Plans(PlanID(key), Capacity)
CustomerInProject(VahedID, cinpid(key))
Vahed(VahedID(key), PlanID,...)

此查询显示人们雇佣的具有相同PlanID（地图）的房屋数量：

select 
    count(*) 
from
    Vahed as v2,
    CustomerInProject 
where 
    CustomerInProject.VahedID = v2.VahedID
group by PlanID

Plans有一个名为int的{{1}}字段。我想从上面的查询中减去Capacity。我怎么能这样做？

Answer 1

这样的事情应该这样做：

select p.PlanID, count(*) - p.Capacity
from Vahed as v2
join CustomerInProject c
  on c.VahedID = v2.VahedID
join Plan p
  on p.PlanID = c.PlanID /* or v.PlanID, it's not clear from the question */
group by p.PlanID, p.Capacity

在第6行，您可能希望将c.PlanID替换为v.PlanID - 我不知道确切的表格架构。

Answer 2

    select sum(cnt)
    from
    (select capacity*-1  as cnt from
    plans
    union 
    select count(*)  as cnt from Vahed as v2
inner join 
      CustomerInProject  on 
        CustomerInProject.VahedID = v2.VahedID
         group by PlanID )

从count（*）查询中减去字段的值

2 个答案: