create function change_region() returns trigger as $change_region$
       declare
            delta_price   real;
	    old_nation    integer;
            new_nation    integer;
            old_region    record;
            new_region    record;
       begin
           old_nation := OLD.s_nationkey;
           new_nationkey := NEW.s_nationkey;
           select into old_region n_regionkey from nation where n_nationkey=old_nation;
           select into new_region n_regionkey from nation where n_nationkey=new_nation;
           if (old_region.n_regionkey=1) then
                if (new_region.n_regionkey=2) then
                     delta_price:=0.8;
                else if (new_region.n_regionkey=3) then
                     delta_price:=1.05;
                end if;
           else if (old_region.n_regionkey=2) then
                if (new_region.n_regionkey=1) then
                     delta_price:=1.2;
                else if (new_region.n_regionkey=3) then
                     delta_price:=1.1;
                end if;
            else if (old_region.n_regionkey=3) then
                if (new_region.n_regionkey=1) then
                     delta_price:=0.8;
                else if (new_region.n_regionkey=2) then
                     delta_price:=0.9;
                end if;
            end if;
            update partsupp set ps_supplycost=ps_supplycost*delta_price where ps_suppkey=NEW.s_suppkey;
            return null;
       end;
$change_region* language plpgsql;