选择对行求和的查询并将其作为列返回

Question

奇怪的问题......我知道。所以让我解释一下。

这是我的文本表

    quota     |    metric_id
     100      |        1
     20       |        2
     100      |        15
     50       |        1
     30       |        2
     20       |        15
     50       |        1
     200      |        2
     10       |        15

我想要一个返回以下

的SELECT语句

    id_1    |     id_2     |      id_15 
    200     |     250      |      130

以下是数据：

Column `id_1` is sum of the 3 rows where `metric_id=1`
Column `id_2` is sum of the 3 rows where `metric_id=2`
Column `id_15` is sum of the 3 rows where `metric_id=15`

任何帮助？

Answer 1

试试这个

select SUM(case when metric_id = 1 then quota END) id_1
       SUM(case when metric_id = 2 then quota END) id_2
       SUM(case when metric_id = 15 then quota END) id_15
FROM Table1

Answer 2

一种可能的方法：

SELECT SUM(quota * (metric_id = 1)) AS id_1,
       SUM(quota * (metric_id = 2)) AS id_2,
       SUM(quota * (metric_id = 15)) AS id_15
FROM Table1

Demo。这很简单：metric_id = N对于具有该属性等于N的行为1，对于所有其他行为0。将quota乘以1是quota，乘以0 - 0，其余的是SUM()函数的简单任务。