0

我在这里遇到问题，我不明白有关该主题的帖子。所以这是我的问题：

在我的应用程序中，我有以下实体：

Customer( CustomerId int, Name varchar(200), Email varchar(100), ...)
Employee (EmployeeId int, Name varchar(200), Email varchar(100), ...)
Sale(SaleId int, CustomerId int, EmployeeId int, SaleDate datetime, ...) Join Table

我怎样才能得到表中每个客户的最后一笔销售？

示例（示例数据）：

Customer:
    1, John Smith, jonh@smith.com, ...
    2, Michael Jackson, michael@jackson.com, ...
    3, Bill Clinton, bill@clinton.com, ...

Employee:
   1, Steve Jobs, steve@jobs.com, ...
   2, Bill Gates, bill@gates.com, ...
   3, Mark Zuckerberg, mark@zuckerberg.com, ...

Sales:
   1, 1 (John Smith), 1 (Steve Jobs), '2013-01-02'
   2, 1 (John Smith), 2 (Bill Gates), '2013-01-11'
   3, 1 (John Smith), 3 (Mark Zuckerberg), '2012-12-25'
   4, 2 (Michael Jackson), 2 (Bill Gates), '2012-11-02'
   5, 2 (Michael Jackson), 1 (Steve Jobs), '2013-01-13'
   6, 3 (Bill Clinton), 3 (Mark Zuckerberg), '2013-01-17'
   7, 3 (Bill Clinton), 2 (Bill Gates), '2011-12-20'

我的结果查询必须给我带来以下结果：

   2, 1 (John Smith), 2 (Bill Gates), '2013-01-11'
   5, 2 (Michael Jackson), 1 (Steve Jobs), '2013-01-13'
   6, 3 (Bill Clinton), 3 (Mark Zuckerberg), '2013-01-17'
4

1 回答 1

1

既然您提到您正在使用SQL Server，请使用Common Table Expression和Window Function

WITH latestRecords
AS
(
    SELECT  SaleId , CustomerId, EmployeeId , SaleDate,
            DENSE_RANK() OVER (PARTITION BY CustomerId
                                ORDER BY SaleDate DESC) RN
    FROM    Sale
)
SELECT  a.SaleId,
        b.Name AS CustomerName,
        c.Name as EmployeeName,
        a.SaleDate
FROM    latestRecords a
        INNER JOIN Customer b
            ON a.CustomerID = b.CustomerID
        INNER JOIN Employee c
            ON a.EmployeeID = c.EmployeeID
WHERE   a.RN = 1
于 2013-01-21T13:38:35.817 回答