来自非规范化表的信息

Question

我有一个表，它是客户表和订单表的组合。它看起来像这样：

_______________________________________________________
| Id | Cust Id  | Other Id | Date | Has Prod 1 | Has Prod 2 |
-------------------------------------------------------
| 1  |          | 1        | 2009 | False      | True       |
| 2  | 1        |          | 2008 | False      | True       |
| 3  | 2        |          | 2008 | True       | False      |
| 4  | 1        |          | 2009 | True       | True       |
| 5  | 2        |          | 2009 | False      | False      |
| 6  | 1        |          | 2010 | False      | True       |
-------------------------------------------------------

我知道我是否有客户的唯一方法是在Cust Id列中找到客户ID。 Cust Id和Other Id指向与此讨论无关的其他表。

我想做两件事：

我想制作一份报告或表格，总结客户并执行“Has”列的逻辑“或”，例如：

_________________________________________________
| Id | Cust Id  | Other Id | Has Prod 1 | Has Prod 2 |
-------------------------------------------------
| 1  | 1        |          | True       | True       |
| 2  | 2        |          | True       | False      |
-------------------------------------------------

我想获取每个Cust Id组中的最新行，例如：

_______________________________________________________
| Id | Cust Id  | Other Id | Date | Has Prod 1 | Has Prod 2 |
-------------------------------------------------------
| 5  | 2        |          | 2009 | False      | False      |
| 6  | 1        |          | 2010 | False      | True       |
-------------------------------------------------------

提前致谢。 GRB

Answer 1

SELECT [Cust ID], MIN([Has Prod 1]) AS MinOne, MIN([Has Prod 2]) AS MinTwo
FROM customerorder
GROUP BY [Cust ID]

MIN（）返回最小值。 -1为True，0为False，因此如果分组行的一条记录为True，则返回-1。

SELECT t1.*
FROM customerorder AS t1
INNER JOIN (SELECT [Cust ID], Max([Date]) As MaxDate
            FROM customerorder 
            GROUP BY [Cust ID]) AS t2
ON ([t1].[Cust ID] = [t2].[Cust ID] AND [t1].[Date] = [t2].[MaxDate])

如果最后一行由Max（[Date]）确定，如示例数据所示，则上述查询将返回每个客户的最后一行。