What are the heights of the people?
select height from people
What is the average?
select avg(height) from people
What are the heights of the body builders?
select t2.height from body_builder as t1 join people as t2 on t1.people_id = t2.people_id
For those results, which ones have weight larger than 91.0?
select t2.height from body_builder as t1 join people as t2 on t1.people_id = t2.people_id where t2.weight > 91.0
What about the total score is smaller than 315?
select t2.height from body_builder as t1 join people as t2 on t1.people_id = t2.people_id where t1.total < 315