Question

我有一个如下所示的Access表：

ID      Country       Application Date
--------------------------------
12      France        12/01/2016
12      Germany       01/01/2017
13      Germany       01/02/2017
14      Spain         23/01/2017
14      Germany       01/02/2017
15      
16      Greece        01/01/2017

我希望每个ID都有一个最近的申请日期。

我试过了：

SELECT ID, Country, Max(Application Date)
FROM MyTable
GROUP BY ID

但是Access拒绝了这个查询，并希望我在group by子句中添加国家/地区，然后才能工作。此外，我希望能够获取没有国家和申请日期的行（比如ID = 15的行）。

预期结果将是：

ID      Country       Application Date
--------------------------------
12      Germany       01/01/2017
13      Germany       01/02/2017
14      Germany       01/02/2017
15      
16      Greece        01/01/2017

Answer 1

我认为这是你想要的

select t1.* from MyTable as t1 inner join
(
SELECT ID, Max(Application Date) as Application Date
FROM MyTable
GROUP BY ID
) as t2 on t1.Id=t2.ID and t1.Application Date=t2.Application Date

Answer 2

它适用于您的输入数据并返回正确的输出数据。试试吧，请）

SELECT d.id, MyTable.country, d.datemax
FROM (SELECT ID as id, Max(AppDate) as datemax
FROM MyTable
GROUP BY ID) as d 
,MyTable
WHERE d.id = MyTable.id and datemax = MyTable.appdate
OR (datemax is null and country is null)

SQL：按原因分组

2 个答案: