HackerRank로 SQL 공부하기 - Top Earners

문제: 모든 직원의 최대 총 수입과 최대 총 수입을 가진 직원의 총 수를 찾아라.

SELECT months * salary, COUNT(*)
FROM Employee
group by months * salary
order by months * salary desc
limit 1;

서브쿼리를 사용한 방법

SELECT MAX(months * salary), COUNT(*)
FROM Employee
WHERE (months * salary) = (SELECT MAX(months * salary) FROM Employee);

select salary*months, count(*) from employee
where salary*months = (select max(salary*months)from employee)
group by salary*months

select salary*months as a, count(*) from employee
group by a
having a = (select max(salary*months) from employee)

정답!