SQL - 构建迭代表

Question

我对表的迭代有疑问。库存中有状态产品 (test_product) 和操作：添加或从库存中删除。

product	action	operation_date	number	total
test_product	add	2023-01-03	4	4
test_product	remove	2023-01-05	-3	1
test_product	remove	2023-01-07	-1	0

有一天我们会添加或删除产品、产品数量和总数。

我想计算天数，在某个时期总人数是0，比方说从2023-01-01到2023-01-10起始值为 total 的列是 0。

在我看来，我有这样的表格：

calendar_day	product	action	operation_day	number	total
2023-01-01					0
2023-01-02					0
2023-01-03	test_product	add	2023-01-03	4	4
2023-01-04					4
2023-01-05	test_product	remove	2023-01-05	-3	1
2023-01-06					1
2023-01-07	test_product	remove	2023-01-07	-1	0
2023-01-08					0
2023-01-09					0
2023-01-10					0

0天数是技术操作，现在不重要了。问题是建表。

我试过这样的事情：

GO
DECLARE @PRODUCT AS VARCHAR(30)
SET @PRODUCT = 'test_product'
DECLARE @TOTAL AS INT
SET @TOTAL = 0
DECLARE @STOP_DATE AS DATE;
SET @STOP_DATE = CAST('2023-01-10' AS DATE)
DECLARE @UP_DATE AS DATE;
SET @UP_DATE = CAST('2023-01-01' AS DATE);
WHILE @STOP_DATE >= @UP_DATE
BEGIN  
SELECT
@UP_DATE AS calendar_day,
CASE
WHEN operation_date = @UP_DATE THEN operation_date
ELSE ''
END AS operation_date,
number,
@TOTAL+number AS total
FROM stock
JOIN products ON products.id = stock.product_id
WHERE products.name = @PRODUCT
AND stock.operation_date >= @UP_DATE
AND stock.operation_date <= @UP_DATE
SET @UP_DATE = DATEADD(DAY, 1, @UP_DATE)
END

但是我得到了分离结果，其中 7 个是空的而且速度太慢，因为我们现在有 9000 个项目。

你能帮助我吗？

Answer 1

您可以分两步完成此任务：

• 用递归查询构建一个日历表，停止在calen_date < '2023-10-01'
• 左加入日历表和您的产品表
• 为每个非空值后跟空值计算分区
• 将每个分区的最大值分配给总计

WITH calendar AS (
    SELECT CAST('2023-01-01' AS DATE) AS calendar_day
    UNION ALL 
    SELECT DATEADD(DAY, 1, calendar_day) FROM calendar WHERE calendar_day < '2023-01-10'
), product_and_calend AS (
    SELECT *, 
           COUNT(CASE WHEN total IS NOT NULL THEN 1 END) OVER(ORDER BY calendar_day) AS num_nulls
    FROM      calendar     c
    LEFT JOIN test_product p
           ON c.calendar_day = p.operation_date
)
SELECT calendar_day, product, action_, operation_date, number,
       COALESCE(MAX(total) OVER(PARTITION BY num_nulls), 0) AS total
FROM product_and_calend

输出：

calendar_day	product	action	operation_day	number	total
2023-01-01					0
2023-01-02					0
2023-01-03	test_product	add	2023-01-03	4	4
2023-01-04					4
2023-01-05	test_product	remove	2023-01-05	-3	1
2023-01-06					1
2023-01-07	test_product	remove	2023-01-07	-1	0
2023-01-08					0
2023-01-09					0
2023-01-10					0

查看演示 here。