What is the average height of players born between 1990 and 1995?
average height = DIVIDE(SUM(height), COUNT(id)); players born between 1990 and 1995 refers to birthday > = '1990-01-01 00:00:00' AND birthday < '1996-01-01 00:00:00';
SELECT SUM(height) / COUNT(id) FROM Player WHERE SUBSTR(birthday, 1, 4) BETWEEN '1990' AND '1995'