累计报表

create table t_access_times(username string,month string,salary int)
row format delimited fields terminated by ',';

load data local inpath '/home/hadoop/t_access_times.dat' into table t_access_times;

create table t_access_times(username varchar(40),month varchar(30),salary int);

insert into t_access_times values('A','2015-01',5);
insert into t_access_times values('A','2015-01',15);
insert into t_access_times values('B','2015-01',5);
insert into t_access_times values('A','2015-01',8);
insert into t_access_times values('B','2015-01',25);
insert into t_access_times values('A','2015-01',5);
insert into t_access_times values('A','2015-02',4);
insert into t_access_times values('A','2015-02',6);
insert into t_access_times values('B','2015-02',10);
insert into t_access_times values('B','2015-02',5);


1、第一步，先求个用户的月总金额
select username,month,sum(salary) as salary from t_access_times group by username,month

+-----------+----------+---------+--+
| username  |  month   | salary  |
+-----------+----------+---------+--+
| A         | 2015-01  | 33      |
| A         | 2015-02  | 10      |
| B         | 2015-01  | 30      |
| B         | 2015-02  | 15      |
+-----------+----------+---------+--+

2、第二步，将月总金额表 自己连接 自己连接
+-------------+----------+-----------+-------------+----------+-----------+--+
| a.username  | a.month  | a.salary  | b.username  | b.month  | b.salary  |
+-------------+----------+-----------+-------------+----------+-----------+--+
| A           | 2015-01  | 33        | A           | 2015-01  | 33        |
| A           | 2015-01  | 33        | A           | 2015-02  | 10        |
| A           | 2015-02  | 10        | A           | 2015-01  | 33        |
| A           | 2015-02  | 10        | A           | 2015-02  | 10        |
| B           | 2015-01  | 30        | B           | 2015-01  | 30        |
| B           | 2015-01  | 30        | B           | 2015-02  | 15        |
| B           | 2015-02  | 15        | B           | 2015-01  | 30        |
| B           | 2015-02  | 15        | B           | 2015-02  | 15        |
+-------------+----------+-----------+-------------+----------+-----------+--+

3、第三步，从上一步的结果中
进行分组查询，分组的字段是a.username a.month
求月累计值：  将b.month