right jion
和on匹配，以后面的表为基准
select last_name,first_name,dept_no from (employees as a) right join (dept_emp as b) on b.emp_no=a.emp_no;

inner join
可以和where一起。
select last_name,first_name,dept_no from (employees as a) inner join (dept_emp as b) where b.emp_no=a.emp_no;