如何使用分组依据和在一起

Question

我有以下数据集

id  name   units  release_date
1   salil   1    2012-04-02
2   salil   2    2012-03-21
3   salil   3    2012-04-02
4   salil   4    2012-03-02
5   salil   5    2012-04-02
6   xyz     1    2012-04-01
7   xyz     2    2012-03-30
8   xyz     3    2012-03-30
9   xyz     4    2012-04-01

我想要每个名称的最长日期的单位总和。 像下面这样

name  units     Max(release_date)
salil  9          2012-04-02
xyz    5          2012-04-01

我尝试追踪，但无法运作

SELECT name, MAX(release_date) as date, sum(units) as units FROM reports

 GROUP BY name;

Answer 1

请尝试以下方法：

    SELECT name, sum(units) as units 
    FROM reports as r
    LEFT JOIN (select max(date) as maxdate from reports group by name ) as mr
    ON r.date=mr.maxdate
    WHERE artist_name='Pacer1'  GROUP BY name;