查找所有员工的last_name和first_name以及对_牛客题霸

有一个员工表，employees简况如下: emp_no birth_date first_name last_name gender hire_date 10001 1953-09-02 Georgi Facello M 1986-06-26 10002 1964-06-02 Bezalel Simmel F 1985-11-21 10003 1959-12-03 Parto Bamford M 1986-08-28 10004 1954-05-01 Christian Koblick M 1986-12-01 有一个部门表，dept_emp简况如下: emp_no dept_no from_date to_date 10001 d001 1986-06-26 9999-01-01 10002 d002 1989-08-03 9999-01-01 请你查找所有已经分配部门的员工的last_name和first_name以及dept_no，也包括暂时没有分配具体部门的员工，以上例子如下: last_name first_name dept_no Facello Georgi d001 Simmel Bezalel d002 Bamford Parto NULL Koblick Chirstian NULL

示例1

输入

drop table if exists  `dept_emp` ; 
drop table if exists  `employees` ; 
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 `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`));
INSERT INTO dept_emp VALUES(10001,'d001','1986-06-26','9999-01-01');
INSERT INTO dept_emp VALUES(10002,'d002','1996-08-03','9999-01-01');
INSERT INTO employees VALUES(10001,'1953-09-02','Georgi','Facello','M','1986-06-26');
INSERT INTO employees VALUES(10002,'1964-06-02','Bezalel','Simmel','F','1985-11-21');
INSERT INTO employees VALUES(10003,'1959-12-03','Parto','Bamford','M','1986-08-28');
INSERT INTO employees VALUES(10004,'1954-05-01','Chirstian','Koblick','M','1986-12-01');

输出

Facello|Georgi|d001
Simmel|Bezalel|d002
Bamford|Parto|None
Koblick|Chirstian|None