SQL19 - 查找所有员工的last_name和first_name以及对应的dept_name

题目描述:

查找所有员工的last_name和first_name以及对应的dept_name，也包括暂时没有分配部门的员工

CREATE TABLE `departments` (
`dept_no` char(4) NOT NULL,
`dept_name` varchar(40) NOT NULL,
PRIMARY KEY (`dept_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 `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`));

 

难易程度:

中等

 

解答:

select employees.last_name,employees.first_name,departments.dept_name
from employees left join dept_emp
on employees.emp_no = dept_emp.emp_no
left join departments
on dept_emp.dept_no = departments.dept_no