how many hours does each player get to be active for?
select pid,hs from player
what position requires the least playing time?
select ppos from tryout as t1 join player as t2 on t1.pid = t2.pid group by t1.ppos order by min ( t2.hs ) limit 1
what is the the playing time of the mid player ?
select min ( t2.hs ), t1.ppos from tryout as t1 join player as t2 on t1.pid = t2.pid where ppos = 'mid' group by t1.ppos