SELECT  *
FROM employees 
order by hire_date desc limit 1;

SELECT *
FROM employees
WHERE hire_date=
(SELECT hire_date
FROM employees
GROUP BY hire_date
ORDER BY hire_date desc limit 2,1
)

group by 結合語句 對列表的某一項進行結合

order by語句預設按照升序對記錄進行排序

如果希望按照降序進行排序，可以使用DESC

limit子句用於限制查詢結果返回數量，常用於分頁查詢

limit i,n

i:為查詢結果的索引值（預設從0開始），當i=0時可省略i

n：為查詢結果返回的數量

SELECT s.emp_no,salary,from_date,s.to_date,d.dept_no 
FROM salaries AS s 
INNER JOIN dept_manager as d 
on s.emp_no=d.emp_no
ORDER BY s.emp_no

SELECT last_name,first_name,dept_no
FROM employees AS s
INNER JOIN dept_emp as d
on s.emp_no=d.emp_no

select
 
 emp_no,count(emp_no) as t
from salaries
group by emp_no HAVING t>15

SELECT salary
FROM salaries
group by salary
order by salary desc

SELECT emp_no
FROM employees
where emp_no not in
(SELECT emp_no 
 FROM dept_manager );

select e.emp_no,m.emp_no as manager 
from dept_emp as e 
INNER JOIN
 
 dept_manager as m 
on e.dept_no=m.dept_no 
where e.emp_no<>m.emp_no

SELECT *
FROM employees
WHERE emp_no%2=1 and last_name<>'Mary' 
ORDER BY hire_date desc

select title,avg(s.salary) 
from titles as t 
INNER JOIN salaries as s 
on t.emp_no=s.emp_no 
group by title

SELECT emp_no,salary
FROM salaries
where salary=(
SELECT salary
WHERE salaries
GROUP BY salary 
order by salary desc LIMIT 1,1)

SELECT e.last_name,e.first_name,s.dept_name 
FROM employees AS e 
LEFT JOIN dept_emp AS d 
ON e.emp_no=d.emp_no 
LEFT JOIN departments AS s 
ON s.dept_no = d.dept_no

SELECT d.dept_no,d.dept_name,count(s.salary) AS sum 
FROM departments AS d 
INNER JOIN dept_emp AS e 
ON d.dept_no= e.dept_no 
INNER JOIN salaries AS s 
ON e.emp_no = s.emp_no 
GROUP BY d.dept_no,d.dept_name 
ORDER BY d.dept_no