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_39 (round INTEGER, position VARCHAR, pick__number VARCHAR)
### Question:
What is the mean round number for center position when the pick number is less than 23?
### Answer:
SELECT AVG(round) FROM table_name_39 WHERE position = "center" AND pick__number < 23