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 Ref_document_types (document_type_code VARCHAR, document_type_name VARCHAR)
### Question:
List all document type codes and document type names.
### Answer:
SELECT document_type_code, document_type_name FROM Ref_document_types