db={"courses":[{_id:1,title:"maths",members:["p1","p2","s1","s2","s3","s4","s5"]}],"professors":[{_id:"p1",name:"Dr. Johnson"},{_id:"p2",name:"Dr. Wong"}],"students":[{_id:"s1",name:"Alice"},{_id:"s2",name:"Bob"},{_id:"s3",name:"Chuck"},{_id:"s4",name:"Dean"},{_id:"s5",name:"Eve"}]}

db.courses.aggregate([{"$lookup":{"from":"professors","localField":"members","foreignField":"_id","as":"professorsLookup"}},{"$lookup":{"from":"students","localField":"members","foreignField":"_id","as":"studentsLookup"}}])