15.查找employees表emp_no为奇数且last_name不为Mary的员工信息，按照hire_date逆序

法一：使用%

select *
from employees
where emp_no%2 =1
and last_name!='Mary'
order by hire_date desc

补充：不相等有三种表示方式：<>、!=、IS NOT

法二：使用&

SELECT *
FROM employees
WHERE emp_no & 1
AND last_name<>'Mary'
ORDER BY hire_date DESC;