Convert Comma delimited String into Rows

SELECT    REGEXP_SUBSTR(STR, '[^,]+', 1, LEVEL) WORDS
FROM       (SELECT 'AA,BB,CC,A,B,C'STR FROM DUAL)
CONNECT BY REGEXP_SUBSTR(STR, '[^,]+', 1, LEVEL) IS NOT NULL

Duplicate Rows

Select Duplicate rows only

SELECT * FROM  SB_TEST1 A
WHERE  ROWID > (SELECT MIN(ROWID) FROM SB_TEST1 B
                WHERE A.A=B.A)
SELECT *
FROM   SB_TEST1
WHERE  ROWID NOT IN (SELECT MAX(ROWID) FROM SB_TEST1 GROUP BY A)  

Select all rows which considered having duplicate
 
SELECT *
FROM   SB_TEST1
WHERE  A IN (SELECT A FROM SB_TEST1
GROUP BY A HAVING COUNT (*) >1)