Sql 如何找到具有不同特定权重的多个列的平均值？

我需要计算mssql中

值A

、

值B

和

值C

的平均值。
我的问题是，我需要的所有信息都在一行中

每个值都有自己的权重：

(sum of values * weight) / (sum weight):

每一列都可以为空。如果有值但没有权重，则权重为100，
如果有一个权重而没有值，那么当然不考虑具体值

e、 g

第1栏：

(2*100+1*80)/(100+80)= 2.55  ≈ 2.6  

第二栏：

(1*100+2*80)/(100+80)

我走了这么远，得到了没有权重的平均值

select ID, VALUE_A, VALUE_B, VALUE_C, Weight_A, Weight_B, Weight_C,
        (SELECT AVG(Cast(c as decimal(18,1)))
        FROM   (VALUES(VALUE_A),
                      (VALUE_B),
                      (VALUE_C)) T (c)) AS [Average]
FROM table

第二次尝试是选择值之和乘以它们的权重，然后除以它们的权重之和。缺少权重之和。不知道如何添加它

select *, 
    (SELECT SUM(Cast(c as decimal(18,1)))
    FROM   (VALUES(VALUE_A* ISNULL(Weight_A,100)),
                  (VALUE_B* ISNULL(Weight_B,100)),
                  (VALUE_C* ISNULL(Weight_C,100))

    ) T (c)) AS [Average]

FROM table

---

这就是你要找的吗

SELECT SUM(val * COALESCE(w, 100)) / SUM(w) as weighted_average,
       SUM(val * COALESCE(w, 100)) as weighted_sum
FROM table t CROSS APPLY
     (VALUES (t.VALUE_A, t.Weight_A),
             (t.VALUE_B, t.Weight_B),
             (t.VALUE_C, t.Weight_C)
     ) a(val, w)
WHERE a.val IS NOT NULL;

---

这就是平均值的计算方法

    SELECT *
        ,CASE 
            WHEN (W.weight_A + W.Weight_B+ W.Weight_C) = 0
                THEN 0
            ELSE (ISNULL(VALUE_A, 0 * W.Weight_A)
                  + (ISNULL(VALUE_B, 0) * W.Weight_B) 
                  + (ISNULL(VALUE_C, 0) * W.Weight_C)) 
                  / (W.weight_A + w.Weight_B+ W.Weight_C)
            END Average
FROM TABLE t
CROSS APPLY (Select CASE WHEN VALUE_A is null then 0 ELSE ISNULL(Weight_A,100) END [Weight_A]
            ,CASE WHEN VALUE_B is null then 0 ELSE ISNULL(Weight_B,100) END [Weight_B]
            ,CASE WHEN VALUE_C is null then 0 ELSE ISNULL(Weight_C,100) END [Weight_C]) W

---

如果Val为空，是否将重量从总和（w）中排除？查看上面的第二个示例

（1*100+2*80）/（100+80）

，OP似乎想要这种行为。@DanielE。是的，我现在在问题中看到了。这可以通过

WHERE

子句轻松处理。

    SELECT *
        ,CASE 
            WHEN (W.weight_A + W.Weight_B+ W.Weight_C) = 0
                THEN 0
            ELSE (ISNULL(VALUE_A, 0 * W.Weight_A)
                  + (ISNULL(VALUE_B, 0) * W.Weight_B) 
                  + (ISNULL(VALUE_C, 0) * W.Weight_C)) 
                  / (W.weight_A + w.Weight_B+ W.Weight_C)
            END Average
FROM TABLE t
CROSS APPLY (Select CASE WHEN VALUE_A is null then 0 ELSE ISNULL(Weight_A,100) END [Weight_A]
            ,CASE WHEN VALUE_B is null then 0 ELSE ISNULL(Weight_B,100) END [Weight_B]
            ,CASE WHEN VALUE_C is null then 0 ELSE ISNULL(Weight_C,100) END [Weight_C]) W