每天五道MySQL---1

1. 查找最晚入职员工的所有信息

    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`));
   ---------------------------------
   select * from employees order by hire_date desc limit 1 

2. 查找入职员工时间排名倒数第三的员工所有信息

   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`));
   ----------------------------------
   select * from employees order by hire_date desc limit 1 offset 2(offset:第几行记录，从0开始)

3. 查找所有已经分配部门的员工的last_name和first_name

   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`));
   ------------------------------------
   select last_name,first_name,dept_no 
   from dept_emp join  employees
   on dept_emp.emp_no = employees.emp_no

4. 查找所有员工的last_name和first_name以及对应部门编号dept_no，也包括展示没有分配具体部门的员工

   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`));
   ---------------------------------
   select last_name,first_name,dept_no 
   from employees left join  dept_emp
   on dept_emp.emp_no = employees.emp_no

5. 查找所有员工入职时候的薪水情况，给出emp_no以及salary， 并按照emp_no进行逆序

   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`));
   ---------------------------------
   select e.emp_no,salary 
   from employees e left join salaries s
   on e.emp_no = s.emp_no
   and e.hire_date = s.from_date
   order by e.emp_no desc