在每个GROUP BY组中选择第一行？

问题：

As the title suggests, I'd like to select the first row of each set of rows grouped with a GROUP BY . 顾名思义，我想选择以GROUP BY分组的每组行的第一行。

Specifically, if I've got a purchases table that looks like this: 具体来说，如果我有一个如下的purchases表：

SELECT * FROM purchases;

My Output: 我的输出：

id | customer | total
---+----------+------
 1 | Joe      | 5
 2 | Sally    | 3
 3 | Joe      | 2
 4 | Sally    | 1

I'd like to query for the id of the largest purchase ( total ) made by each customer . 我想查询每个customer购买的最大商品的id （ total ）。 Something like this: 像这样：

SELECT FIRST(id), customer, FIRST(total)
FROM  purchases
GROUP BY customer
ORDER BY total DESC;

Expected Output: 预期产量：

FIRST(id) | customer | FIRST(total)
----------+----------+-------------
        1 | Joe      | 5
        2 | Sally    | 3

---

解决方案：

参考一： https://stackoom.com/question/FwhD/在每个GROUP-BY组中选择第一行
参考二： https://oldbug.net/q/FwhD/Select-first-row-in-each-GROUP-BY-group

来源：oschina

链接：https://my.oschina.net/u/4428122/blog/4492109