我有以下数据(实际上跨越了数年,但在此示例中,我只包括了4个月)
id created_at staff
--------------------------------
1 2010-01-01 Coder
2 2010-01-15 Developer
3 2010-03-01 Data Analyst
4 2010-01-20 Developer
5 2010-03-13 Data Analyst
6 2010-04-05 Tester
7 2010-04-01 Tester
8 2010-04-04 Business Analyst
9 2010-01-22 Business Analyst
10 2010-01-25 Coder
我想创建一个查询,该查询计算staff
每个年月的数量。下面是我期望从该查询中获得的输出示例。
staff 2010-01 2010-02 2010-03 2010-04
----------------------------------------------------------
Coder 2 0 0 0
Developer 2 0 0 0
Data Analyst 0 0 2 0
Tester 0 0 0 2
Business Analyst 1 0 0 1
任何帮助是极大的赞赏!
对于固定的月份列表,可以进行条件汇总:
select staff,
sum(case when date_trunc('month', created_at) = date '2010-01-01' then 1 else 0 end) as cnt_2010_01,
sum(case when date_trunc('month', created_at) = date '2010-02-01' then 1 else 0 end) as cnt_2010_02,
sum(case when date_trunc('month', created_at) = date '2010-03-01' then 1 else 0 end) as cnt_2010_03,
sum(case when date_trunc('month', created_at) = date '2010-04-01' then 1 else 0 end) as cnt_2010_04
from mytable
group by staff
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