SQL选择具有公共值的组

Question

我正在摸索如何做这个选择。

表（GroupID，参与者）
g1，A
g1，B
g2，A
g2，C
g3，A
g3，B
g3，C
g4，A
g4，B
g4，C
g4，D

我想选择只有A，B，C共享的GroupID（在这种情况下，将是g3）。请注意，我不想要g4，因为我想要只有A，B，C所在的GroupID。任何帮助都将不胜感激。

Answer 1

这将选择至少有3个不同groupid

的participants个

select groupid
from your_table
group by groupid
having count(distinct participants) >= 3

要明确A,B,C，您可以

select groupid
from your_table
where participants in ('A','B','C')
group by groupid
having count(distinct participants) = 3

如果您不想要任何其他参与者，那么

select groupid
from your_table
group by groupid
having sum(participants = 'A') > 0
and sum(participants = 'B') > 0
and sum(participants = 'C') > 0
and sum(participants not in ('A','B','C')) = 0

或

select groupid
from your_table
group by groupid
having sum(participants not in ('A','B','C')) = 0
and count(distinct participants) = 3