SQL Lite 中具有多个条件和列的 AVG 函数

Question

我想出了如何使用 condition/s 执行 avg 函数，但我无法让它满足我的特定需求。假设我正在使用这个名为 sales_performance

的 table

  product_ID  sales_period  sales_qty  sales_index  product_sub goal_met
         C12          0001         15           20          D71        Y
         D71          0001         07           09          C12        N
         F20          0001         25           30          C05        Y
         C05          0001         10           15          F20        N
         C12          0002         15           30          C05        Y
         C05          0002         12           06          C12        N
         D71          0002         30           20          F20        Y
         F20          0002         20           15          D71        N
         C12          0003         05           04          F20        N
         F20          0003         40           35          C12        Y
         D71          0003         20           20          C05        Y
         C05          0003         12           10          D71        N

我想为产品 C12 计算一个名为 sales_index_goal 的新值。然后，此值的公式为：

average of sales_index of product 'C12' when Goal_Met = 'Y' and the sales_index of its sub_product when Goal_Met = 'N' during the sales periods before that one.

例如，如果我想为产品 'C12' 计算 sales_period 0003 的 sales_index_goal，它将计算为：

average of (30,20,15) where 30 and 20 are the sales_indexes of product 'C12' in sales periods 1 and 2 and 15 is the sales_index of Product 'F20' in sales period 2.

我在计算确切销售期间的这个值时没有遇到任何问题。但是，我很难想出一个查询来计算所有销售期间产品 'C12' 的这个值。目前，我写了这个不起作用的查询：

SELECT 
    s.*, 
    AVG(CASE 
        WHEN s2.goal_met = "Y" AND s2.product_id = "C2" 
            THEN s2.sales_index 
        WHEN s2.product_id = (
            SELECT s2.product_sub WHERE s2.product_id = "C12"
        ) AND s2.goals_met = "N" 
            THEN s2.sales_index
        ELSE NULL 
    END)
    OVER (
        ORDER BY s.sales_period 
        ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
    ) AS sales_index_goal
FROM 
    sales_performance s, 
    sales_performance s2
WHERE s.product_id = "C12"

如果能提供任何帮助，我将不胜感激。奖励：为所有销售期间的所有产品计算此值。

编辑：下面的答案适用于计算产品 C12 的 sales_index_goal 但是，它不适用于产品 F20（为什么它不起作用的更详细原因在我在答案下方的评论中) 可以看到商品F20的查询结果here

Answer 1

使用 window 函数是一个很好的起点。一个问题在于您想要对来自不同列的值取平均值，并且这些值可能具有不同的出现次数。

我认为您需要分解计算以计算平均值：对值求和，然后除以出现次数的总和。

考虑：

SELECT *
FROM (
    SELECT 
        s.*,
        (
            0.0 + 
            COALESCE(SUM(CASE WHEN goal_met = 'Y' THEN sales_index END) OVER(
                PARTITION BY product_id 
                ORDER BY sales_period 
                ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
            ), 0)
            + COALESCE(SUM(CASE WHEN goal_met = 'N' THEN sales_index END) OVER(
                PARTITION BY product_sub 
                ORDER BY sales_period 
                ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
            ), 0)
        ) / (
            COALESCE(SUM(goal_met = 'Y') OVER(
                PARTITION BY product_id 
                ORDER BY sales_period 
                ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
            ), 0)
            + COALESCE(SUM(goal_met = 'N') OVER(
                PARTITION BY product_sub 
                ORDER BY sales_period 
                ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
            ), 0)
        ) AS sales_index_goal
    FROM sales_performance s
) x WHERE product_ID = 'C12'

在 this DB fiddle 中，使用您的样本数据，这个 returns:

| product_ID | sales_period | sales_qty | sales_index | product_sub | goal_met | sales_index_goal   |
| ---------- | ------------ | --------- | ----------- | ----------- | -------- | ------------------ |
| C12        | 1            | 15        | 20          | D71         | Y        |                    |
| C12        | 2            | 15        | 30          | C05         | Y        | 20                 |
| C12        | 3            | 5         | 4           | F20         | N        | 21.666666666666668 |

Answer 2

不确定这是否真的需要 window 功能。

下面的示例只是自链接 table 并按 C12 产品分组。

CREATE TABLE sales_performance
(
 product_ID varchar(3) not null,
 sales_period varchar(4) not null,
 sales_qty char(2) not null,
 sales_index char(2) not null,
 product_sub char(3) not null,
 goal_met char(1)  not null,
 PRIMARY KEY (product_ID, sales_period)
)

INSERT INTO sales_performance
(product_ID,sales_period,sales_qty,sales_index,product_sub,goal_met) 
VALUES
 ('C12','0001','15','20','D71','Y')
,('D71','0001','07','09','C12','N')
,('F20','0001','25','30','C05','Y')
,('C05','0001','10','15','F20','N')
,('C12','0002','15','30','C05','Y')
,('C05','0002','12','06','C12','N')
,('D71','0002','30','20','F20','Y')
,('F20','0002','20','15','D71','N')
,('C12','0003','05','04','F20','N')
,('F20','0003','40','35','C12','Y')
,('D71','0003','20','20','C05','Y')
,('C05','0003','12','10','D71','N')
;

SELECT c12.*, sub.sales_index
FROM sales_performance c12
LEFT JOIN sales_performance sub 
  ON sub.sales_period < c12.sales_period 
 AND 
 (
    (sub.product_ID = c12.product_sub AND sub.goal_met = 'N') OR
    (sub.product_ID = c12.product_ID AND sub.goal_met = 'Y')
 )
WHERE c12.product_id = 'C12'
ORDER BY c12.product_ID, c12.sales_period, sub.product_ID

product_ID | sales_period | sales_qty | sales_index | product_sub | goal_met | sales_index
:--------- | :----------- | :-------- | :---------- | :---------- | :------- | :----------
C12        | 0001         | 15        | 20          | D71         | Y        | null       
C12        | 0002         | 15        | 30          | C05         | Y        | 15         
C12        | 0002         | 15        | 30          | C05         | Y        | 20         
C12        | 0003         | 05        | 04          | F20         | N        | 20         
C12        | 0003         | 05        | 04          | F20         | N        | 30         
C12        | 0003         | 05        | 04          | F20         | N        | 15

SELECT 
 c12.*
 , ROUND(AVG(sub.sales_index),1) AS sales_index_goal
FROM sales_performance c12
LEFT JOIN sales_performance sub 
  ON sub.sales_period < c12.sales_period 
 AND 
 (
    (sub.product_ID = c12.product_sub AND sub.goal_met = 'N') OR
    (sub.product_ID = c12.product_ID AND sub.goal_met = 'Y')
 )
WHERE c12.product_id = 'C12' 
GROUP BY c12.product_ID, c12.sales_period
ORDER BY c12.product_ID, c12.sales_period;

product_ID | sales_period | sales_qty | sales_index | product_sub | goal_met | sales_index_goal
:--------- | :----------- | :-------- | :---------- | :---------- | :------- | :---------------
C12        | 0001         | 15        | 20          | D71         | Y        | null            
C12        | 0002         | 15        | 30          | C05         | Y        | 17.5            
C12        | 0003         | 05        | 04          | F20         | N        | 21.7

db<>fiddle here

SQL Lite 中具有多个条件和列的 AVG 函数

AVG function with multiple conditions and columns in SQL Lite

sql

sqlite

conditional

average