如何 select 给定 ID 和日期的最后一个非空值

Question

我正在尝试 select 列中非空白（技术上不是非空）的最后一个值，并在之后的每个日期 select 它，直到该值发生变化，然后 select 该值等等。

我有：

company_id	date	sales_stage	previous_sales_stage
1	2022-05-20 00:00:00.000	a	NULL
1	2022-05-19 00:00:00.000	b	NULL
1	2022-05-18 00:00:00.000	c	NULL
1	2022-05-17 00:00:00.000	c	NULL
1	2022-05-16 00:00:00.000	c	NULL
1	2022-05-15 00:00:00.000	d	NULL
1	2022-05-14 00:00:00.000	d	NULL
1	2022-05-13 00:00:00.000	d	NULL
1	2022-05-12 00:00:00.000	e	NULL
1	2022-05-11 00:00:00.000	e	NULL

我想要的：

company_id	date	sales_stage	previous_sales_stage
1	2022-05-20 00:00:00.000	a	b
1	2022-05-19 00:00:00.000	b	c
1	2022-05-18 00:00:00.000	c	d
1	2022-05-17 00:00:00.000	c	d
1	2022-05-16 00:00:00.000	c	d
1	2022-05-15 00:00:00.000	d	e
1	2022-05-14 00:00:00.000	d	e
1	2022-05-13 00:00:00.000	d	e
1	2022-05-12 00:00:00.000	e	NULL
1	2022-05-11 00:00:00.000	e	NULL

这是一份摘要 table，与所有公司共享（因此在给定日期会有多个公司 ID 和阶段）并且每天从存储过程中计算。如果没有值，NULL也可以。

这里有一些 T-SQL 来创建一个临时 table 来重新创建这个例子：

DROP TABLE IF EXISTS #blah

    CREATE TABLE #blah
(
    company_id INT
  , [date] DATETIME
  , sales_stage VARCHAR(50)
  , previous_sales_stage VARCHAR(50)
);


INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'a',CAST(GETDATE() AS DATE))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'b',dateadd(d,-1,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'c',dateadd(d,-2,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'c',dateadd(d,-3,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'c',dateadd(d,-4,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'d',dateadd(d,-5,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'d',dateadd(d,-6,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'d',dateadd(d,-7,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'e',dateadd(d,-8,cast(getdate() as date)))
INSERT INTO #blah (company_id, sales_stage, [date]) VALUES (1,'e',dateadd(d,-9,cast(getdate() as date)))


SELECT * FROM #blah

UPDATE #blah SET previous_sales_stage = 'b' WHERE company_id = 1 AND date = '2022-05-20 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'c' WHERE company_id = 1 AND date = '2022-05-19 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'd' WHERE company_id = 1 AND date = '2022-05-18 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'd' WHERE company_id = 1 AND date = '2022-05-17 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'd' WHERE company_id = 1 AND date = '2022-05-16 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'e' WHERE company_id = 1 AND date = '2022-05-15 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'e' WHERE company_id = 1 AND date = '2022-05-14 00:00:00.000'
UPDATE #blah SET previous_sales_stage = 'e' WHERE company_id = 1 AND date = '2022-05-13 00:00:00.000'
UPDATE #blah SET previous_sales_stage = NULL WHERE company_id = 1 AND date = '2022-05-12 00:00:00.000'
UPDATE #blah SET previous_sales_stage = NULL WHERE company_id = 1 AND date = '2022-05-11 00:00:00.000'

SELECT * FROM #blah

Answer 1

您可以使用子查询或外部应用，如下所示：

SELECT t1.company_id, t1.date, t1.sales_stage, x.previous_sales_stage
FROM #blah t1
OUTER APPLY (
    SELECT TOP 1 t2.sales_stage AS previous_sales_stage
    FROM #blah t2 
    WHERE t2.company_id=t1.company_id
        AND t2.date<t1.date
        AND t2.sales_stage<>t1.sales_stage
    ORDER BY t2.date DESC
) x

如何 select 给定 ID 和日期的最后一个非空值

How do I select the last non-empty value for a given ID and date

sql

tsql

sql-server

sql-server-2019