SCOTT@orcl_11g> CREATE OR REPLACE FUNCTION no_dups
  2    (p_string IN VARCHAR2)
  3    RETURN VARCHAR2
  4  AS
  5    v_string_in   VARCHAR2 (32767) := p_string || '^';
  6    v_value	     VARCHAR2 (32767);
  7    v_string_out  VARCHAR2 (32767);
  8  BEGIN
  9    WHILE LENGTH (v_string_in) > 1 LOOP
 10  	 -- identify first value in incoming string:
 11  	 v_value := SUBSTR (v_string_in, 1, INSTR (v_string_in, '^'));
 12  	 -- concatenate first value to output string:
 13  	 v_string_out := v_string_out || v_value;
 14  	 -- replace all such values in incoming string:
 15  	 v_string_in := REPLACE (v_string_in, v_value, '');
 16  	 -- repeat loop with next value until no values left
 17    END LOOP;
 18    -- return output string:
 19    RETURN RTRIM (v_string_out, '^');
 20  END no_dups;
 21  /

Function created.

SCOTT@orcl_11g> SHOW ERRORS
No errors.
SCOTT@orcl_11g> SELECT no_dups ('IAN^ANDREW^KEVIN^IAN^ANDREW') FROM DUAL
  2  /

NO_DUPS('IAN^ANDREW^KEVIN^IAN^ANDREW')
--------------------------------------------------------------------------------
IAN^ANDREW^KEVIN

SCOTT@orcl_11g>