获取所有员工的emp_no、部门编号dept_no以及对应的bonus类型btype和received，没有分配奖金的员工不显示对应的bonus类型btype和received CREATE TABLE `dept_emp` ( `emp_no` int(11) NOT NULL, `dept_no` char(4) NOT NULL, `from_date` date NOT NULL, `to_date` date NOT NULL, PRIMARY KEY (`emp_no`,`dept_no`)); CREATE TABLE `emp_bonus`( emp_no int(11) NOT NULL, received datetime NOT NULL, btype smallint(5) NOT NULL); CREATE TABLE `employees` ( `emp_no` int(11) NOT NULL, `birth_date` date NOT NULL, `first_name` varchar(14) NOT NULL, `last_name` varchar(16) NOT NULL, `gender` char(1) NOT NULL, `hire_date` date NOT NULL, PRIMARY KEY (`emp_no`)); 返回的结果格式如下: e.emp_no dept_no btype received 10001 d001 1 2010-01-01 10002 d001 2 2010-10-01 10003 d004 3 2011-12-03 10004 d004 1 2010-01-01 10005 d003 10006 d002 10007 d005 10008 d005 10009 d006 10010 d005 10010 d006