Counting Duplicate Record SQL on single Table

SELECT   INSTITUTE_ID, SL_NO, ROOM_NO, SIZE_NO, class_name, 
COUNT (*) dup_rec    FROM   class_rooms GROUP BY
INSTITUTE_ID, SL_NO, ROOM_NO, SIZE_NO, class_name  HAVING   COUNT (*) > 1
and INSTITUTE_ID is not null and SL_NO is not null and
ROOM_NO is not null and SIZE_NO is not null and   class_name is not null
order by INSTITUTE_ID desc, SL_NO, ROOM_NO, SIZE_NO, class_name;


























select INSTITUTE_ID, SL_NO, ROOM_NO, SIZE_NO, class_name from
class_rooms where institute_id=35065 and class_name='Six' order by institute_id;


SELECT INSTITUTE_ID, SL_NO, ROOM_NO, SIZE_NO, class_name,
COUNT(*) OVER(PARTITION BY INSTITUTE_ID, SL_NO, ROOM_NO, SIZE_NO, class_name) AS NumberOfDuplicates
FROM CLASS_ROOMS;