DECLARE @Table TABLE (Name CHAR(3), DOB DATE, Score INT)
INSERT INTO @Table VALUES ('Ant',GETDATE(),10),('Bob',GETDATE()-1,10),('Mum', GETDATE()-2,5)
SELECT * FROM @Table

;with RowNumber as
(
SELECT ROW_NUMBER() OVER(ORDER BY Score DESC) AS RowNum, Name, DOB, Score FROM @Table
)
select * from RowNumber where RowNum = 1

;with ranking as
(
SELECT RANK() OVER(ORDER BY Score DESC) AS RowNum,Name, DOB, Score FROM @Table
)
SELECT * from ranking where RowNum = 1

;with dense_ranking as
(
SELECT DENSE_RANK() OVER(ORDER BY Score DESC) AS RowNum,Name,DOB,Score FROM @Table
)
SELECT * FROM dense_ranking WHERE RowNum = 1

;with ntileing as
(
SELECT NTILE(2) OVER(ORDER BY Score DESC) AS RowNum, Name, DOB, Score FROM @Table
)
SELECT * FROM ntileing WHERE RowNum = 1

SELECT DT.max_score, A.name, a.dob
FROM dbo.Exam A
	INNER JOIN (SELECT MAX(score) max_score
			FROM dbo.Exam
			) DT ON DT.max_score = A.score