create or replace procedure add_region(p_phone_num in out varchar2)
as
begin
p_phone_num :='021-'||p_phone_num;
end;
/** ----------执行
declare
v_phone_num varchar2(15);
begin
v_phone_num := '39117380';
add_region(v_phone_num);
dbms_output.put_line('new phone is:'||v_phone_num);
end;
*/