Show names for all aircrafts of which John Williams has certificates.
create table aircraft (name varchar, aid varchar, PRIMARY KEY (name)); create table employee (eid varchar, name varchar, PRIMARY KEY (eid)); create table certificate (eid varchar, aid varchar, PRIMARY KEY (eid))
select t3.name from employee as t1 join certificate as t2 on t1.eid = t2.eid join aircraft as t3 on t3.aid = t2.aid where t1.name = "john williams"