my_decimal *Item_ref::val_decimal(my_decimal *decimal_value)
{
  my_decimal *val= (*ref)->val_decimal_result(decimal_value);
  null_value= (*ref)->null_value;
  return val;
}
my_decimal *Item_ref::val_decimal(my_decimal *decimal_value)
{
  my_decimal *val= (*ref)->val_decimal_result(decimal_value);
  null_value= (*ref)->null_value;
  return val;
}