如何在SQL中將一行與其他行進行比較

Question

我有一個由團隊成員組成的數據集。

我只想計算成員2的平均值。

但是，滿足計算的條件如下：

例如，id 1讓Anna和Sam一起工作，我只想為member2（即Sam）計算

為此，我想對具有

• 山姆和他一起工作，像id:2 member1:Sam member2:Sam
• Sam與其他成員（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

輸入項

+----+---------+---------+-------+
| 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 |
+----+---------+---------+-------+

輸出量

+----+---------+---------+-------+-----+
| 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

請嘗試以下操作：

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