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_49 (round INTEGER, position VARCHAR, overall VARCHAR)
### Question:
What is the average round when there is a defensive back and an overall smaller than 199?
### Answer:
SELECT AVG(round) FROM table_name_49 WHERE position = "defensive back" AND overall < 199