Cannot exeute DML in a function

Question

I have a function as follows,
CREATE OR REPLACE FUNCTION get_cns(
sysc IN ib_fact_batchno.SYS_CODE%TYPE,
subc IN ib_fact_batchno.SUB_CODE%TYPE)
RETURN Varchar2 AS
rowcnt NUMBER;
curn varchar2(10);
BEGIN
LOCK TABLE ib_fact_batchno IN ROW EXCLUSIVE MODE;
SELECT COUNT(*) INTO rowcnt FROM ib_fact_batchno
WHERE SYS_CODE = sysc AND SUB_CODE = subc;
IF (rowcnt = 0) THEN
INSERT INTO ib_fact_batchno VALUES (sysc, subc, '1');
ELSE
UPDATE ib_fact_batchno SET CUR_NUM = TO_CHAR(TO_NUMBER(CUR_NUM)+1)
WHERE SYS_CODE = sysc AND SUB_CODE = subc;
END IF;
SELECT CUR_NUM INTO curn FROM ib_fact_batchno
WHERE SYS_CODE = sysc AND SUB_CODE = subc;
COMMIT;
RETURN
END;
the creation is success. But when I use it as
select get_cns('CUS', '807') from dual;
I have the following error:
ERROR 在行 1:
ORA-14551: 無法在查詢內執行 DML 作業
ORA-06512: 在 "ADMIN.GET_CNS", line 15
ORA-06512: 在 line 1
What's the problem? and How to fix it?
BR/Jean

Answer 1

Firstly, please post technical questions in the specific forums : General Database Discussions
To answer your question, The function is fine, the SELECT statement select get_cns('CUS', '807') from dual; is incorrect.
In case you are just trying to test if the function get_cns is working fine, you could use an anonymous PL/SQL block as follows :
set serveroutput on
declare
temp varchar2(100);
begin
temp := get_cns('CUS', '807');
dbms_output.put_line(temp);
end;