What is Zach age?
select age from person where name = "Zach"
Yes
select name from person where job = "doctor"
Who is in the town of new york?
select name from person where city = "new york city"
Who has friends that are younger than the average age?
select distinct t2.name from person as t1 join personfriend as t2 on t1.name = t2.friend where t1.age < ( select avg ( age ) from person )