SQL分组查询示例-优快云博客

本文提供了一个SQL分组查询的实际案例，展示了如何通过多个子查询来汇总不同月份的数据，并按用户名进行分组，以便更好地理解和应用SQL聚合函数。

有如下数据：
日期          姓名金额
2008-1-12 sun 100
2008-1-12 张    100
2008-1-13 sun 100
2008-1-19 张    300
2008-2-12 sun 120
2008-2-19 张    300
2008-3-12 sun 130

得到的查询结果：
姓名    2008-01    2008-02   2008-03
sun      200           120         130
张        400           300

我的答案(非最佳答案.)

select t1.username "姓名","2009-09","2009-10","2009-11"
from (select username,sum(money) as "2009-09" from SCOTT.MY where datetime between to_date('2009-09-01','yyyy-mm-dd') and to_date('2009-09-30','yyyy-mm-dd') group by username) t1,
(select username,sum(money) as "2009-10" from SCOTT.MY where datetime between to_date('2009-10-01','yyyy-mm-dd') and to_date('2009-10-30','yyyy-mm-dd') group by username) t2,
(select username,sum(money) as "2009-11" from SCOTT.MY where datetime between to_date('2009-11-01','yyyy-mm-dd') and to_date('2009-11-30','yyyy-mm-dd') group by username) t3
where t1.username = t2.username and t2.username = t3.username;