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 table_name_51 (doctor_who_episode VARCHAR, original_airdate__uk_ VARCHAR)
### Question:
Which Doctor Who episode has a Original airdate (UK) of dvd only?
### Answer:
SELECT doctor_who_episode FROM table_name_51 WHERE original_airdate__uk_ = "dvd only"