Need pl/sql stmnts. for this simple logic

Question

Hi,
I need PL/SQL program for this simple logic i am doing mistake somewhere unbale to trace
out ..
select * from GSR03_PO_DTL;
PO_NUM
L53177000 -- > no changes reqd (only one entry with new format)
L00041677 --> to be updated to L41677000(only one entry with OLD format)
L43677000 -- > no change reqd (exists one row with new format and old format like below)
L00043677 -- > to be deleted this is old format (and new format like above already exists)
EX:
L00012345 --- old format
L12345000 --- new format
Hope question is clear. I written the following program.
update is working fine but delete is not working.
Please help.
Thanks in Advance
Devender
declare
Cursor c_test is
(select po_num from GSR03_PO_DTL);
BEGIN
FOR r_test in c_Test
LOOP
dbms_output.put_line (r_test.po_num);
IF ('L'||substr(r_test.po_num,5,5)) = ('L'||substr(r_test.po_num,2,5)) then
     dbms_output.put_line ('delete stmnt');
END IF;     
EXIT WHEN c_test%NOTFOUND;
END LOOP;
FOR r_test in c_Test
LOOP
IF r_test.po_num like 'L000%' then
IF ('L'||substr(r_test.po_num,5,5)) is not NULL then
     update GSR03_PO_DTL set PO_NUM = 'L'||substr(po_num,5,5)||'000'
     where po_num like 'L000%' ;
     dbms_output.put_line ('update stmnt');
END IF;     
END IF;
END LOOP;
END;
*********************

Answer 1

No need for PL/SQL, man.
SQL> SELECT po_no FROM po1
  2  /
PO_NO
L53177000
L00041677
L43677000
L00043677
SQL> UPDATE po1 y
  2  SET    y.po_no = 'L'||substr(y.po_no,5,5)||'000'
  3  WHERE  y.po_no LIKE 'L000%'
  4  AND    NOT EXISTS ( SELECT null FROM po1 x
  5                      WHERE x.po_no =  'L'||substr(y.po_no,5,5)||'000')
  6  /
1 row updated.
SQL> DELETE FROM po1 y
  2  WHERE  y.po_no LIKE 'L000%'
  3  AND    EXISTS ( SELECT null FROM po1 x
  4                  WHERE x.po_no =  'L'||substr(y.po_no,5,5)||'000')
  5  /
1 row deleted.
SQL> SELECT po_no FROM po1
  2  /
PO_NO
L53177000
L41677000
L43677000
SQL> Cheers, APC