Что делать, если вы хотите начать с университета, а не колледжа?
ю MongoDB за последние два дня, и я пытаюсь объединить три коллекции, но не могу этого достичь
Ниже приведены четыре коллекции, ведущие в базе данных
Университет
{
"_id" : "5834ecf7432d92675bde9d82",
"name": "NIFT"
}
колледж
{
"_id" : "5834ecf7432d92675bde9d83",
"name": "NIFT Hyderabad",
"university_id":"5834ecf7432d92675bde9d82"
}
ведомства
{
"_id" : "5834ecf7432d92675bde9d84",
"department_name": "Fashion Technology",
"college_id" : "5834ecf7432d92675bde9d83"
},
{
"_id" : "5834ecf7432d92675bde9d85",
"department_name": "Merchandising",
"college_id" : "5834ecf7432d92675bde9d83"
}
Разделы
{
"_id" : "5834ecf7432d92675bde9d86",
"section_name": "A",
"students" : "56",
"department_id":"5834ecf7432d92675bde9d84"
},
{
"_id" : "5834ecf7432d92675bde9d87",
"section_name": "B",
"students" : "60",
"department_id":"5834ecf7432d92675bde9d84"
},
{
"_id" : "5834ecf7432d92675bde9d86",
"section_name": "A",
"students" : "55",
"department_id":"5834ecf7432d92675bde9d85"
},
{
"_id" : "5834ecf7432d92675bde9d87",
"section_name": "B",
"students" : "44",
"department_id":"5834ecf7432d92675bde9d85"
}
Здесь я пытаюсь добиться вывода в следующем формате
Ожидаемый результат
[{
"_id": "5834ecf7432d92675bde9d83",
"name": "NIFT Hyderabad",
"university_id": "5834ecf7432d92675bde9d82",
"departments": [{
"_id": "5834ecf7432d92675bde9d84",
"department_name": "CSE",
"college_id": "5834ecf7432d92675bde9d83",
"sections": [{
"_id": "5834ecf7432d92675bde9d86",
"section_name": "A",
"students": "56",
"department_id": "5834ecf7432d92675bde9d84"
}, {
"_id": "5834ecf7432d92675bde9d87",
"section_name": "B",
"students": "60",
"department_id": "5834ecf7432d92675bde9d84"
}]
},
{
"_id": "5834ecf7432d92675bde9d85",
"department_name": "Mechanical",
"college_id": "5834ecf7432d92675bde9d83",
"sections": [{
"_id": "5834ecf7432d92675bde9d86",
"section_name": "A",
"students": "55",
"department_id": "5834ecf7432d92675bde9d85"
},
{
"_id": "5834ecf7432d92675bde9d87",
"section_name": "B",
"students": "44",
"department_id": "5834ecf7432d92675bde9d85"
}
]
}
]
}]
Но я получаю отдел и разделы в отдельных массивах для колледжа, но не могу получить как в вышеуказанном формате
запрос
db.college.aggregate([
{"$match": { "university_id": "5834ecf7432d92675bde9d82" } },
{"$lookup": {
"localField": "_id",
"from": "departments",
"foreignField": "college_id",
"as": "departments"
}},
{"$unwind":"$departments"},
{$group : {_id : "$_id", departments : {$push : "$departments" }}},
{"$lookup": {
"localField": "departments._id",
"from": "sections",
"foreignField": "department_id",
"as": "sections"}
}
])
Может ли кто-нибудь помочь мне решить эту проблему, это будет очень полезно для меня.