Oracle 11g Release 2

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CREATE TABLE table_name ( name ) AS
  SELECT 'Hari'    FROM DUAL UNION ALL
  SELECT 'Hari'    FROM DUAL UNION ALL
  SELECT 'Hari'    FROM DUAL UNION ALL
  SELECT 'Alice'   FROM DUAL UNION ALL
  SELECT 'Bob'     FROM DUAL UNION ALL
  SELECT 'Bob'     FROM DUAL UNION ALL
  SELECT 'Charlie' FROM DUAL;
7 rows affected

MERGE INTO table_name dst
USING (
  SELECT ROWID AS rid,
         name,
         ROW_NUMBER() OVER ( PARTITION BY name ORDER BY ROWNUM ) AS rn
  FROM   table_name
) src
ON ( dst.ROWID = src.rid )
WHEN MATCHED THEN
  UPDATE SET name = CASE rn
                    WHEN 1
                    THEN src.name
                    ELSE src.name || '-' || (rn - 1)
                    END;
7 rows affected

ALTER TABLE table_name ADD CONSTRAINT table_name__name__u UNIQUE( name );
SELECT * FROM table_name;


NAME


Hari

Hari-1

Hari-2

Alice

Bob

Bob-1

Charlie