What is the average height of all players?
select avg(height) from player
What is the average height of players from 'University of Akron'?
select avg(t1.height) from player as t1 join player_college as t2 on t1.player_id = t2.player_id join college as t3 on t3.college_id = t2.college_id where t3.name_full = 'University of Akron';
How about for those from Yale University?
select avg(t1.height) from player as t1 join player_college as t2 on t1.player_id = t2.player_id join college as t3 on t3.college_id = t2.college_id where t3.name_full = 'Yale University'