多列的平均值

Question

我有一个名为Request的表,数据看起来像:

Req_ID    R1   R2   R3   R4   R5

R12673    2    5    3    7    10
R34721    3    5    2    1    8
R27835    1    3    8    5    6

现在我想显示R1,R2,R3,R4和R5的平均值

所以我写了一个像这样的查询:

Select Req_ID, Avg(R1+R2+R3+R4+R5) as Average
from Request
Group by Req_ID

但我得到R1,R2,R3,R4和R5的总和不是平均值？我在哪里做错了.

Answer 1

您没有提到列是否可以为空.如果它们是,并且您想要AVG聚合提供的相同语义(2008)

SELECT *,
       (SELECT AVG(c)
        FROM   (VALUES(R1),
                      (R2),
                      (R3),
                      (R4),
                      (R5)) T (c)) AS [Average]
FROM   Request  

2005版本有点单调乏味

SELECT *,
       (SELECT AVG(c)
        FROM   (SELECT R1
                UNION ALL
                SELECT R2
                UNION ALL
                SELECT R3
                UNION ALL
                SELECT R4
                UNION ALL
                SELECT R5) T (c)) AS [Average]
FROM   Request

Answer 2

如果数据存储为INT,您可能想尝试

Average = (R1 + R2 + R3 + R4 + R5) / 5.0