Создание ссылок

Заполняем коллекцию для хранения школ:

db.schools.insert({schoolNumber: 218, schoolName: "School A"});
db.schools.insert({schoolNumber: 444, schoolName: "School B"});
db.schools.insert({schoolNumber: 123, schoolName: "School C"});

Заполняем коллекцию для хранения учеников:

db.pupils.insert({pupilName: "Maxim", pupilSchool: 218});
db.pupils.insert({pupilName: "George", pupilSchool: 218});
db.pupils.insert({pupilName: "Nina", pupilSchool: 444});
db.pupils.insert({pupilName: "Alice", pupilSchool: 444});
db.pupils.insert({pupilName: "Ann", pupilSchool: 123});

Получаем описание школы для каждого ученика:

cursor = db.pupils.find().sort({pupilSchool: 1}); null;
while(cursor.hasNext()) {
    pupilObj = cursor.next();
    numberOfSchool = pupilObj['pupilSchool'];
    schoolObj = db.schools.findOne({schoolNumber: parseInt(numberOfSchool)});
    nameOfSchool = schoolObj['schoolName'];
    nameOfPupil = pupilObj['pupilName'];
    s = nameOfPupil + " : " + schoolObj['schoolNumber'] + " : " + nameOfSchool;
    print(s);
}

Результат работы программы:

Ann : 123 : School C
Maxim : 218 : School A
George : 218 : School A
Nina : 444 : School B
Alice : 444 : School B