HackerRank[MySQL] : New Companies

New Companies

Q

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, Lead_Manager L, Senior_Manager S, Manager M, Employee E
WHERE C.company_code = L.company_code AND
      L.lead_manager_code = S.lead_manager_code AND
      S.senior_manager_code = M.senior_manager_code AND
      M.manager_code = E.manager_code 
GROUP BY C.company_code, C.founder
ORDER BY C.company_code