Vanaf versie 3.2 kunt u $lookup in aggregatiepijplijn om left outer join uit te voeren.
Student.aggregate([{
$lookup: {
from: "worksnapsTimeEntries", // collection name in db
localField: "_id",
foreignField: "student",
as: "worksnapsTimeEntries"
}
}]).exec(function(err, students) {
// students contain WorksnapsTimeEntries
});