Show names for all employees who have certificates on both Boeing 737-800 and Airbus A340-300.
select t1.name from employee as t1 join certificate as t2 on t1.eid = t2.eid join aircraft as t3 on t3.aid = t2.aid where t3.name = "Boeing 737-800" intersect select t1.name from employee as t1 join certificate as t2 on t1.eid = t2.eid join aircraft as t3 on t3.aid = t2.aid where t3.name = "Airbus a340-300"