Question

我在预订表中有如下所示的数据集

oldornewapp

我正在尝试输出显示基于每个客户的custid MaxApptDateOldApp MaxapptDatenewapp --------------------------------------------- 100 01-jan-2014 12-oct-2016 200 01-feb-2015 10-oct-2016列的最长日期

{{1}}

请告诉我获取结果集的最佳方法，我使用的是SQL Server 2012

提前致谢

Answer 1

SELECT
    Custid
    ,MAX(CASE WHEN oldornewApp = 'old' THEN ApptDate END) as MaxApptDateOldApp
    ,MAX(CASE WHEN oldornewApp = 'new' THEN ApptDate END) as MaxApptDateNewApp
FROM
    TableName
GROUP BY
    Custid

您可以使用条件聚合来获得所需的结果。

Answer 2

您可以使用

加入和分组

select old.Custid, max(old.ApptDate) as MaxApptDateOldApp, max(new.ApptDate) as MaxApptDateNewApp
from my_table as old
where a.oldornewApp = 'old';
group by a,Custid
inner join  (
    select b.Custid, max(b.ApptDate) as AppDate
    from my_table as b
    where b.oldornewApp = 'new';
    group by b.Custid
) new

SQL Server列max基于另一列

2 个答案: