自用题解
查找所有员工的last_name和first_name以及对应的dept_name
http://www.nowcoder.com/questionTerminal/5a7975fabe1146329cee4f670c27ad55
select `e`.`last_name`,`e`.`first_name`,`depa`.`dept_name` from ( `employees` as `e` left join `dept_emp` as `de` on `e`.`emp_no`=`de`.`emp_no` ) left join `departments` as `depa` on `depa`.`dept_no`=`de`.`dept_no`