Five MySQL --- 1 day

1. Find all the information at the latest recruits

    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. Find recruits ranked third time information of all employees

   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. Find all the staff have been assigned sectors last_name and 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. Find all employees last_name and first_name and the corresponding department number dept_no, but also show employees are not assigned specific sectors

   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. Find the entry salary of all employees when given emp_no and salary, and in reverse order according to emp_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`));
   ---------------------------------
   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