sql - 找到每艘船上的水手

Question

我不知道如何以通用的方式解释这个问题，所以我将发布具体案例:

我有 3 张 table :

水手们:

S(ids, names, rating, age)

船:

B(idb, nameb, color)

预订:

Bo(ids, idb, date)

我必须编写一个查询来查找预订了每艘船的所有水手。

即使我发布了一个特定的案例，我也想要一个可以应用于同类问题的通用答案。

提前谢谢您。

Answer 1

您可以通过以下查询获取预订了每艘船的水手的 ID:

select ids
from bookings
group by ids
having count(distinct idb) = (select count(*) from boats)

因此可以将其与运算符 IN 一起使用:

select * from sailors
where ids in (
    select ids
    from bookings
    group by ids
    having count(distinct idb) = (select count(*) from boats)
)

或加入水手:

select s.*
from sailors s 
inner join (
    select ids
    from bookings
    group by ids
    having count(distinct idb) = (select count(*) from boats)
) t on t.ids = s.ids