已知原表(t_salary)
year salary
2000 1000
2001 2000
2002 3000
2003 4000
先要实现显示结果(salary为以前的工资和)
year salary
2000 1000
2001 3000

答案：

select year, (select sum(salary) from t_salary b where b.year <= a.year) salary from t_salary a
group by year