Hi All

i have problem in Trigger functoin


when trigger  fire then ERROR massage is

ERROR :  Attribute 'UNDEF00' not found
PostgreSQL status:PGRES_FATAL_ERROR

here UNDEF00 is by defult value of po_no
TRIGGER IS

CREATE TRIGGER add_stock_gr_trig  AFTER UPDATE on gr FOR EACH ROW execute procedure add_stock_gr_fun();      
my function is this

create function add_stock_gr_fun() returns opaque as'
DECLARE
   rec RECORD;
   txtpo varchar;
BEGIN

IF NEW.po_no <> "UNDEF00" THEN   
           SELECT INTO rec  gr_no, noofbags, final_wt, matl_cd
           FROM po p, gr g
           WHERE g.po_no=p.po_no and g.gr_no=NEW.gr_no;   

            IF OLD.po_no #= "UNDEF00" THEN
                        UPDATE matl_mst
                        SET bal_bag = bal_bag + rec.noofbags,  
                        bal_kg = bal_kg + rec.final_wt  
                       WHERE matl_mst.matl_cd = rec.matl_cd;
            ELSE
                        UPDATE matl_mst
                        SET bal_bag = bal_bag + NEW.noofbags - OLD.noofbags,    
                        bal_kg = bal_kg + NEW.final_wt  - OLD.final_wt
                       WHERE matl_mst.matl_cd = rec.matl_cd;
                        
            END IF;
END IF;

return NULL;    




END;'  language 'plpgsql';      




please Help me


Ramesh Patel