CREATE OR REPLACE PROCEDURE dupes AS
 
CURSOR dupes_cur IS
SELECT task_code, ROWID
FROM jwc_task_code_test
ORDER BY task_code;
 
dupes_rec dupes_cur%ROWTYPE;
 
prev_val      VARCHAR2(100);
cur_val      VARCHAR2(100);
 
 
BEGIN
 
OPEN dupes_cur;
prev_val := '';
 
     LOOP
 
          FETCH dupes_cur INTO dupes_rec;
          EXIT WHEN dupes_cur%notfound;
 
 
          IF prev_val = dupes_rec.task_code
          THEN 
               DELETE 
               FROM jwc_task_code_test
               WHERE ROWID = dupes_rec.ROWID;
          ELSE NULL;
          END IF;
 
          prev_val :=  dupes_rec.task_code;
 
     END LOOP;
 
CLOSE dupes_cur;
 
END dupes;
 
--------------------------------------------------
// Another method, courtesy Mariusz Gesicki
 
 
DELETE TABLE_WITH_DUPS twd
       WHERE twd.ID IN (SELECT t2.ID
       FROM (SELECT ROW_NUMBER() OVER (PARTITION BY
t1.TASK_CODE ORDER BY t1.ID NULLS LAST) AS
DUP_NUMBER, t1.ID
       FROM TABLE_WITH_DUPS t1
       ORDER BY t1.TASK_CODE) t2
       WHERE t2.DUP_NUMBER > 1);