SQL60 统计salary的累计和running_total

1 CREATE TABLE `salaries` ( `emp_no` int(11) NOT NULL,
2 `salary` int(11) NOT NULL,
3 `from_date` date NOT NULL,
4 `to_date` date NOT NULL,
5 PRIMARY KEY (`emp_no`,`from_date`));

1 select emp_no, salary,
2 
3 ( select sum(salary) from salaries as s2 where s1.emp_no >= s2.emp_no and  s2.to_date = ‘9999-01-01‘ ) as running_total
4 
5 from salaries as s1
6 
7 where s1.to_date = ‘9999-01-01‘ ;