18.Highest Peak Name and Elevation by Country

SELECT TOP (5) p.CountryName AS Country  ,
ISNULL(P.PeakName,'(no highest peak)') AS [Highest Peak Name]
,ISNULL( P.Elevation,0) AS[Highest Peak Elevation],
isnull(P.MountainRange, '(no mountain)' ) AS Mountain
FROM

(SELECT c.CountryName,p.PeakName, p.Elevation ,
DENSE_RANK() OVER(partition BY c.CountryName ORDER BY
p.Elevation DESC) AS Rank, M.MountainRange
FROM Countries c
LEFT JOIN MountainsCountries mc ON C.CountryCode=
mc.CountryCode
LEFT JOIN Mountains m ON m.id= mc.MountainId
LEFT  JOIN Peaks p ON P.MountainId= M.Id)
AS P
WHERE RANK=1