如何在SQL中将一行与其他行进行比较

Question

我有一个由团队成员组成的数据集。

我只想计算成员2的平均值。

但是，满足计算的条件如下：

例如，id 1让Anna和Sam一起工作，我只想为member2（即Sam）计算

为此，我想对具有

• 山姆和他一起工作，像id:2 member1:Sam member2:Sam
• Sam与其他成员（而不是Anna（member1））一起工作，例如id:3 member1:Sam member2:Nihal或id:4 member1:Nihal member2:Sam

然后除以不同的#ID

输入项

+----+---------+---------+-------+
| ID | member1 | member2 | score |
+----+---------+---------+-------+
|  1 | Anna    | Sam     |    10 |
|  2 | Sam     | Sam     |    30 |
|  3 | Sam     | Nihal   |    40 |
|  4 | Nihal   | Sam     |    50 |
|  5 | Sam     | Anna    |    20 |
|  6 | Anna    | Anna    |    60 |
|  7 | Nihal   | May     |    70 |
|  8 | May     | May     |    80 |
+----+---------+---------+-------+

输出量

+----+---------+---------+-------+-----+
| ID | member1 | member2 | score | AVG |
+----+---------+---------+-------+-----+
|  1 | Anna    | Sam     |    10 |  40 |-->AVG= 30+40+50/3
|  2 | Sam     | Sam     |    30 |  30 |-->AVG= score
|  3 | Sam     | Nihal   |    40 |  70 |-->AVG= 70/1
|  4 | Nihal   | Sam     |    50 |  20 |-->AVG= 30+10+20/3
|  5 | Sam     | Anna    |    20 |  60 |-->AVG= 60/1
|  6 | Anna    | Anna    |    60 |  60 |-->AVG= score
|  7 | Nihal   | May     |    70 |  80 |-->AVG= 80/1
|  8 | May     | May     |    80 |  80 |-->AVG= score
+----+---------+---------+-------+-----+

Answer 1

请尝试以下操作：

select t1.*,q.avg_score
from yourtable t1
cross apply
(
    select avg(score) as avg_score
    from yourtable t2
    where 
        t1.member2 in (t2.member1,t2.member2)
        and t1.member1 not in  (t2.member1,t2.member2)
)q