IF (OBJECT_ID('tempdb..#Oceny') IS NOT NULL) DROP TABLE #Oceny
CREATE TABLE #Oceny (OcenaID bigint, Ocena varchar(20))
INSERT INTO #Oceny
VALUES(1, '1')
, (2, '2')
, (3, '3')
, (4, '3.5')
, (5, '4')
, (6, '4.5')
, (7, '5')

IF (OBJECT_ID('tempdb..#Uczniowie') IS NOT NULL) DROP TABLE #Uczniowie
CREATE TABLE #Uczniowie (UczenID bigint, OcenaID bigint)
INSERT INTO #Uczniowie
VALUES(1, 3)
, (1, 5)
, (2, 6)
, (3, 4)
, (4, 3)
, (5, 8)
, (6, 9)

SELECT *
FROM #Oceny AS O
INNER JOIN #Uczniowie AS U ON O.OcenaID = U.OcenaID

SELECT *
FROM #Oceny AS O
LEFT JOIN #Uczniowie AS U ON O.OcenaID = U.OcenaID

SELECT *
FROM #Oceny AS O
RIGHT JOIN #Uczniowie AS U ON O.OcenaID = U.OcenaID

SELECT *
FROM #Uczniowie AS U
LEFT JOIN #Oceny AS O ON O.OcenaID = U.OcenaID

SELECT *
FROM  #Uczniowie AS U
RIGHT JOIN #Oceny AS O ON O.OcenaID = U.OcenaID