相关疑难解决方法(0)

正如标题所示,我想选择用a组成的每组行的第一行GROUP BY.

具体来说,如果我有一个purchases看起来像这样的表:

SELECT * FROM purchases;

我的输出:

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

我想查询每个产品id的最大购买量(total)customer.像这样的东西:

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

预期产出:

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

我有这个SQL查询:

SELECT   Foo, Bar, SUM(Values) AS Sum
FROM     SomeTable
GROUP BY Foo, Bar
ORDER BY Foo DESC, Sum DESC

这导致输出类似于:

47  1   100
47  0   10
47  2   10
46  0   100
46  1   10
46  2   10
44  0   2

我想每个Foo只有第一行,而忽略其余的.

47  1   100
46  0   100
44  0   2

我怎么做？