获取所有员工的emp_no

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 `dept_manager` (
`dept_no` char(4) NOT NULL,
`emp_no` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`dept_no`));
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`));
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`));
-- 官网题目缺失表
CREATE TABLE `emp_bonus` (
`emp_no` int not null,
`recevied` datetime not null,
`btype` smallint not null);

select t1.emp_no, dept_no, btype, recevied from (select e.emp_no,dept_no from employees e,dept_emp de where e.emp_no = de.emp_no) t1 left join emp_bonus eb on t1.emp_no = eb.emp_no

select e.emp_no,dept_no from employees e,dept_manager dm where e.emp_no = dm.emp_no