如何使用组BY和HAVING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 

我想要一个单元的每个名称最大日期的总和。像follwing

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

我尝试以下，但它不工作

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

GROUP BY name; 

Answer 1

尝试以下：

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;