有歧义的部分，必须指定表名
查找当前薪水详情以及部门编号dept_no
http://www.nowcoder.com/questionTerminal/c63c5b54d86e4c6d880e4834bfd70c3b
select salaries.emp_no, salary, salaries.from_date, salaries.to_date, dept_no from salaries, dept_manager where dept_manager.to_date='9999-01-01' and salaries.to_date='9999-01-01' and salaries.emp_no=dept_manager.emp_no order by salaries.emp_no asc;