[HackerRank] New Companies

https://www.hackerrank.com/challenges/the-company/problem?isFullScreen=true 

SELECT C.COMPANY_CODE
    , C.FOUNDER
    , COUNT(DISTINCT L.LEAD_MANAGER_CODE)
    , COUNT(DISTINCT S.SENIOR_MANAGER_CODE)
    , COUNT(DISTINCT M.MANAGER_CODE)
    , COUNT(DISTINCT E.EMPLOYEE_CODE)
FROM COMPANY C LEFT JOIN LEAD_MANAGER L
    ON C.COMPANY_CODE = L.COMPANY_CODE
    LEFT JOIN SENIOR_MANAGER S
    ON L.LEAD_MANAGER_CODE = S.LEAD_MANAGER_CODE
    LEFT JOIN MANAGER M
    ON S.SENIOR_MANAGER_CODE = M.SENIOR_MANAGER_CODE
    LEFT JOIN EMPLOYEE E
    ON M.MANAGER_CODE = E.MANAGER_CODE
GROUP BY C.COMPANY_CODE, C.FOUNDER
ORDER BY C.COMPANY_CODE