sql - Postgres 查询代表的年度销售报告。按月分组

Question

我想按销售代表创建一个年度销售报告表，显示所有十二个月。我拥有的数据或多或少类似于此示例:

id | rep | date      | price
----------------------------
1    1     2017-01-01  20
2    1     2017-01-20  44
3    2     2017-02-18  13
4    2     2017-03-08  12
5    2     2017-04-01  88
6    2     2017-09-05  67
7    3     2017-01-31  10
8    3     2017-06-01  74

我需要的结果是这样的:

Rep Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
----------------------------------------------------
1   64  0   0   0   0   0   0   0   0   0   0   0
2   0   13  12  88  0   0   0   0   67  0   0   0
3   10  0   0   0   0   74  0   0   0   0   0   0

编写此查询的最有效方法是什么？

Answer 1

一种方法:

select rep,
sum(case when extract('month' from date) = 1 then price else 0 end ) as Jan,
sum(case when extract('month' from date) = 2 then price else 0 end ) as Feb 
-- another months here
from t
group by rep