关联表的递归自查询（SQL 服务器）

Question

鉴于以下结构和数据，我正在寻找制造商已更改的客户加入：

create table #sale (
    saleid int,
    customerid int,
    productid int,
    saledate date
);
create table #product (
    productId int,
    name varchar(max),
    manufacturerId int
);
create table #manufacturer (
    manufacturerid int,
    name varchar(max)
)

insert into #manufacturer values (1, 'Manufacturer 1');
insert into #manufacturer values (2, 'Manufacturer 2');

insert into #product values (1, 'Product A', 1);
insert into #product values (2, 'Product B', 1);
insert into #product values (3, 'Product C', 2);

insert into #sale values (1, 101, 1, '2013-01-01');
insert into #sale values (2, 101, 2, '2015-04-01');
insert into #sale values (3, 102, 3, '2013-03-01');
insert into #sale values (4, 102, 3, '2015-01-01');
insert into #sale values (5, 103, 1, '2013-01-01');
insert into #sale values (6, 103, 3, '2015-06-01');
insert into #sale values (7, 102, 1, '2015-06-01');

在这种情况下，两个客户换用了不同制造商的产品，理想的结果是这样的：

customerid  previous manufacturer   new manufacturer    date
102         Manufacturer 2          Manufacturer 1      6/1/2015
103         Manufacturer 1          Manufacturer 2      6/1/2015

我一直在尝试使用 CTE，但没有成功。欣赏和见解或指导。

更新 - 我可以忍受在 customerid 上横向扩展一定数量的连接以显示不同的制造商和日期（5-10 个连接）。对我来说，这比使用 CTE 尝试 UNION ALL 容易得多。

谢谢！

Answer 1

查询

WITH X AS 
 (
  SELECT s.*
        ,M.manufacturerid
        ,m.name
        ,ROW_NUMBER() OVER (PARTITION BY s.CustomerID
                            ORDER BY saledate ASC) rn 
  FROM #sale s 
  INNER JOIN #product p      ON s.productid = p.productId
  INNER JOIN #manufacturer m ON p.manufacturerId = m.manufacturerid 
)
SELECT xx.customerid
       ,xy.name        [previous manufacturer]
       ,xx.name        [new manufacturer]
       ,xx.saledate [Date]
FROM x xy
INNER JOIN x xx ON xx.customerid = xy.customerid
               AND xx.rn = xy.rn + 1
               AND xx.manufacturerid <> xy.manufacturerid

结果：

╔════════════╦═══════════════════════╦══════════════════╦════════════╗
║ customerid ║ previous manufacturer ║ new manufacturer ║    Date    ║
╠════════════╬═══════════════════════╬══════════════════╬════════════╣
║        102 ║ Manufacturer 2        ║ Manufacturer 1   ║ 2015-06-01 ║
║        103 ║ Manufacturer 1        ║ Manufacturer 2   ║ 2015-06-01 ║
╚════════════╩═══════════════════════╩══════════════════╩════════════╝

Answer 2

这是使用 LAG 的替代方法：

select customerid,
       [previous manufacturer],
       [new manufacturer],
       saledate
from (
  select s.customerid, 
         m.name as [new manufacturer],
         s.saledate,
         lag(m.name) over (partition by s.customerid order by s.saledate) as [previous manufacturer],
         case when 
           lag(m.manufacturerId) over (partition by s.customerid order by s.saledate) is not null 
           and lag(m.manufacturerId) over (partition by s.customerid order by s.saledate) <> m.manufacturerId
         then 1 else 0
         end as is_manufacturer_change
  from sale s
  join product p on p.productid = s.productid
  join manufacturer m on m.manufacturerid = p.manufacturerid) x
where x.is_manufacturer_change = 1
order by customerid, saledate

SQLFiddle

关联表的递归自查询（SQL 服务器）

Recursive Self Query With Associated Tables (SQL Server)

sql

sql-server

join

recursive-query

查询

结果：