在日期不同时加入日期表

Question

所以基本上我想知道如何在不同的日期加入两个 table。第一个 table 是我的主要 table，其中包括我所有已购买商品的客户。购买日期为过去单点：

Customers
    +--------+----------+-------+------------+
    | custid | Quantity | Price | ReportDate |
    +--------+----------+-------+------------+
    | 371965 |       12 |     2 | 9/1/2016   |
    | 371965 |        2 |     5 | 2/25/2018  |
    | 377958 |       45 |     3 | 9/1/2016   |
    | 270723 |       12 |  1.25 | 5/1/2014   |
    | 270723 |    10.86 |  1.25 | 6/1/2014   |
    | 270723 |    12.29 |   1.3 | 7/1/2014   |
    | 270723 |    12.29 |   1.4 | 9/15/2016  |
    +--------+----------+-------+------------+

所以我想和我的客户 table 一起在 table 上享受折扣。优惠生效的时间基本上是一个完整的时间，直到发布新的优惠：

Discounts
    +----+-----------+----------+
    | id | startdate | discount |
    +----+-----------+----------+
    |  1 | 7/18/2013 |      0.1 |
    |  2 | 1/10/2014 |     0.25 |
    |  3 | 7/11/2016 |     0.11 |
    |  4 | 9/14/2016 |     0.12 |
    |  5 | 1/12/2017 |     0.15 |
    |  6 | 2/6/2017  |     0.22 |
    |  7 | 6/28/2017 |     0.09 |
    +----+-----------+----------+

所以我的目标是 link 两个 table 并查看哪个购买日期落在适当的折扣区间内。这将是我的目标：

+--------+----------+-------+------------+----+-----------+----------+
| custid | Quantity | Price | ReportDate | id | startdate | discount |
+--------+----------+-------+------------+----+-----------+----------+
| 371965 |       12 |     2 | 9/1/2016   |  3 | 7/11/2016 |     0.11 |
| 371965 |        2 |     5 | 2/25/2018  |  7 | 6/28/2017 |     0.09 |
| 377958 |       45 |     3 | 9/1/2016   |  3 | 7/11/2016 |     0.11 |
| 270723 |       12 |  1.25 | 5/1/2014   |  2 | 41649     |     0.25 |
| 270723 |    10.86 |  1.25 | 6/1/2014   |  2 | 1/10/2014 |     0.25 |
| 270723 |    12.29 |   1.3 | 7/1/2014   |  2 | 1/10/2014 |     0.25 |
| 270723 |    12.29 |   1.4 | 9/15/2016  |  4 | 9/14/2016 |     0.12 |
+--------+----------+-------+------------+----+-----------+----------+

Answer 1

您可以使用 OUTER APPLY 到 select 报告日期之前存在的 TOP 1 折扣，按日期降序排列以获得最近的操作

  SELECT C1.*,DQ.*  FROM CUSTOMERS C1 OUTER APPLY 
                 (SELECT TOP 1 D.* FROM Discounts D WHERE C1.ReportDate >= D.startDate  
                                       ORDER BY D.StartDate DESC) DQ

Answer 2

您可以这样加入：

select c.*, d.*
from customers c inner join discounts d
on d.startdate = (select max(startdate) from discounts where startdate <= c.reportdate)

见demo

Answer 3

另一种选择

;with cte as (
Select A.* 
      ,B.*
      ,RN = row_number() over (Partition by custid,reportdate order by startdate desc)
 From Customers A
 Join Discounts B on B.startdate<=A.ReportDate
) 
Select * 
 From  cte 
 Where RN=1

dbFiddle

在日期不同时加入日期表

Join tables on dates when dates are different

sql

sql-server

join

date

period