NEED URGENT HELP....

I am using PostgreSql 8.1 with pgAdmin III. OS is XP.

 

this is my function:

CREATE OR REPLACE FUNCTION sp_get_phase(character varying, character varying, character varying)
  RETURNS ret_dv_sp_get_phase AS
$BODY$
SELECT          BOOK_NO, USER_ID, COMPANY_ID, PHASE, UPDATE_USER_ID, UPDATE_DATE,
                      AddInfo1, AddInfo2
FROM            T_PHASE
WHERE           (USER_ID = $1) AND (COMPANY_ID = $2) AND BOOK_NO IN ($3)
$BODY$
  LANGUAGE 'sql' VOLATILE;


When I run
select * from sp_get_phase ('sandip', 'oms', '4')   returns 1 record.....this works fine....

select * from sp_get_phase ('sandip', 'oms', '1')  returns 1 record.....this also works fine... BUT

select * from sp_get_phase ('sandip', 'oms', '1,4') this return a Blank record.

I tried to execute the SQL statement from the function

SELECT          BOOK_NO, USER_ID, COMPANY_ID, PHASE, UPDATE_USER_ID, UPDATE_DATE,
                      AddInfo1, AddInfo2
FROM            T_PHASE
WHERE           (USER_ID = 'testUser') AND (COMPANY_ID = 'testCompany') AND BOOK_NO IN (1,4)

----- This Works fine... returns 2 records.   What may be the problem?

Thanks in advance.
Regards,
Sandip.