Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE train (ObjectNumber VARCHAR, Railway_ID VARCHAR); CREATE TABLE railway (ObjectNumber VARCHAR, Railway_ID VARCHAR)
### Question:
List the object number of railways that do not have any trains.
### Answer:
SELECT ObjectNumber FROM railway WHERE NOT Railway_ID IN (SELECT Railway_ID FROM train)