State the phone name which has the least price on the list?
select name from phone as t2 order by price asc limit 1
Which phone id has the highest stock on the list?
select phone_id from phone_market order by num_of_stock desc limit 1
For each phone, show its names and total number of stocks?
select t2.name, sum ( t1.num_of_stock ) from phone_market as t1 join phone as t2 on t1.phone_id = t2.phone_id group by t2.name
State the name of the Carrier of Iphone 6s?
select carrier from phone where name = "IPhone 6s"