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I want to implement a function that would process students, courses and instructors data (loaded from MongoDB collections) in order to produce information about students enrolled on courses (and store it in another MongoDB collection). the function reports each student’s:
primary key
their name
the number of courses they are enrolled in
I want to Store the output of this routine in a MongoDB collection called coursereport like this :
[
{
"_id": "jeff",
"value": {
"name": "Jeff Holland",
"numbercourses": 2
}
},
{
"_id": "john.shore",
"value": {
"name": "John Shore",
"numbercourses": 2
}
},
{
"_id": "lee2331",
"value": {
"name": "Lee Aldwell",
"numbercourses": 1
}
},
{
"_id": "rcotter",
"value": {
"name": "Ray Cotter",
"numbercourses": 2
}
},
{
"_id": "scott",
"value": {
"name": "Scott Mills",
"numbercourses": 3
}
}
]
my data :
{
"students": [
{
"_id": "john.shore",
"name": {"first": "John", "last": "Shore"},
"email": "john.shore#gmail.com",
"major": "Electrical Engineering"
},
{
"_id": "jeff",
"name": {"first": "Jeff", "last": "Holland"},
"email": "jeff#yahoo.com",
"major": "Business"
},
{
"_id": "scott",
"name": {"first": "Scott", "last": "Mills"},
"email": "scott#hotmail.com",
"major": "Humanities/Art"
},
{
"_id": "rcotter",
"name": {"first": "Ray", "last": "Cotter"},
"email": "rcotter#msn.com",
"major": "Computer Science"
},
{
"_id": "lee2331",
"name": {"first": "Lee", "last": "Aldwell"},
"email": "lee2331#aol.com",
"major": "Graphic Design"
}
],
"courses": [
{
"_id": "HIST-1010",
"name": "History of the World 1010",
"description": "A bunch of really interesting things that actually happened",
"students": ["scott", "john.shore"],
"ratings": [3, 5, 4, 5, 4, 4, 2, 4]
},
{
"_id": "ENGCOMP-1010",
"name": "English Composition 1010",
"description": "If you can't write well, you've got nothing!",
"students": ["scott", "lee2331", "rcotter", "john.shore", "jeff"],
"ratings": [4, 4, 5, 4, 5, 1, 5]
},
{
"_id": "ART-1050",
"name": "Artistic Interpretation 1050",
"description": "Discover your inner beholder",
"students": ["rcotter", "scott", "jeff"],
"ratings": [3, 4, 3, 4, 4, 3, 4, 4]
}
],
"instructors": [
{
"_id": "wally.r.binns",
"name": {"first": "Wally", "middle": "r", "last": "Binns"},
"email": "wally.r.binns#ssu.edu",
"bio": "I was born in the middle of my mother's doctoral dissertation on Faraday Cage isolation. I've been an academic ever since...",
"publications": [{
"title": "Inverted Celestial Poetry",
"source": "http://www.pubcentral.com/poetry/inverted-celestial-poetry"
}],
"courses": ["ENGLIT-2500"]
},
{
"_id": "gerald.waterford.iii",
"name": {"first": "Gerald", "last": "Waterford", "suffix": "III"},
"email": "gerald.waterford.iii#ssu.edu",
"bio": "My father's father was a great man. My father, not so much. I am restoring the family honor.",
"publications": [{
"title": "Grow, grow, little Dandelion",
"source": "http://www.hopefulstories.com/my-dandelion"
}, {"title": "The teapot and the spoon", "source": "http://www.dishsoap.com/teapot-spoon"}],
"courses": ["ENGCOMP-1010", "HIST-1010"]
},
{
"_id": "kim.b",
"name": {"prefix": "Mrs.", "first": "Kim", "last": "Binnley"},
"email": "kim.b#ssu.edu",
"bio": "My mother told me 'Don't let those dopes push you around'. My life has been a constant struggle against dopeness ever since. Sigh...",
"publications": [],
"courses": ["ART-1050"]
}
]
}
I started with that :
async function produceReport(db, callback) {
const students = db.collection('students');
const courses = db.collection('courses');
const instructors = db.collection('instructors');
// implement missing code that will create 'coursereport' mongo collection with student courses data
callback();
}
module.exports = produceReport;
can any one give a help please
You have to use $lookup
Defined as:
To perform an equality match between a field from the input documents with a field from the documents of the “joined” collection,
So you have to join students and courses and later the output value with instructors..
Take a look at this query:
db.students.aggregate([
{
$lookup: {
from: "courses",
localField: "item",
foreignField: "email",
as: "students_courses"
}
},
{
"$lookup": {
"from": "instructors",
"localField": "students_courses._id",
"foreignField": "courses",
"as": "students_courses"
}
},
{
"$set": {
"_id": "$_id",
"value": {
"name": {
"$concat": [
"$name.first",
" ",
"$name.last"
]
},
"numbercourses": {
"$size": "$students_courses"
}
}
}
},
{
"$project": {
"_id": 1,
"value": 1
}
}
])
First stage is a joing with two collections with the fields indicated and soterd into a field called students_courses.
Then, another join with the _ids from the students_courses.
With the data then you can create a field named value with the name and count the number of courses in other field.
And $project to show only fields you want.
Check an example here
db.students.aggregate([
{
$lookup: {
from: "courses",
localField: "_id",
foreignField: "students",
as: "students_courses"
}
},
{
$project: {
_id: 1,
value: {
name: {
$concat: [
"$name.first",
" ",
"$name.last"
]
},
numbercourses: {
"$size": "$students_courses"
}
}
}
}
])
I am having a challenge getting just the username in a response below. How do I access the username. i can access the other data but this
[
{
"_id": "5f44d450aaa72313549d519f",
"imageTitle": "uuuuu",
"imageDesc": "uuuuu",
"imageControl": "public",
"imageUrl": "http://localhost:3000/uploads/image-1598346320523.jpg",
"userId": {
"local": {
"username": "uuuuu"
},
"_id": "5f44d3e9aaa72313549d519e"
},
"uploadedOn": "2020-08-25T09:05:20.840Z",
"__v": 0
},
{ ....}
]
You can do it like so
var arr = JSON.parse(`
[ { "_id": "5f44d450aaa72313549d519f", "imageTitle": "uuuuu", "imageDesc": "uuuuu", "imageControl": "public", "imageUrl": "http://localhost:3000/uploads/image-1598346320523.jpg", "userId": { "local": { "username": "uuuuu" }, "_id": "5f44d3e9aaa72313549d519e" }, "uploadedOn": "2020-08-25T09:05:20.840Z", "__v": 0 },
{}
]`);
console.log(arr[0].userId.local.username);
If you are on a newer version of node (14.0.0, and up), then I recommend using the optional chaining operator
arr[0].userId?.local?.username
I need to filter some users according to some fixed criteria. I have a user collection and a talent collection. The talent collection holds the reference to a master category collection.
What I need is to filter these users according to the category in the talent collection and some keys from the user collection.
For example I need to search for a user whose gender is 'male' and education 'BTech' and will have talents as a programmer and tester
my user collection is like,
{
"_id": "5f1939239bd35429ac9cd78f",
"isOtpVerified": "false",
"role": "user",
"adminApproved": 1,
"status": 0,
"languages": "Malayalam, Tamil, Telugu, Kannada",
"name": "Test user",
"email": "test#email.com",
"phone": "1234567890",
"otp": "480623",
"uid": 100015,
"bio": "Short description from user",
"dob": "1951-09-07T00:00:00.000Z",
"gender": "Male",
"education": "Btech",
"bodyType": "",
"complexion": "",
"height": "",
"weight": "",
"requests": [],
"location": {
"place": "place",
"state": "state",
"country": "country"
},
"image": {
"avatar": "5f1939239bd35429ac9cd78f_avatar.jpeg",
"fullsize": "5f1939239bd35429ac9cd78f_fullsize.png",
"head_shot": "5f1939239bd35429ac9cd78f_head_shot.jpeg",
"left_profile": "5f1939239bd35429ac9cd78f_left_profile.png",
"right_profile": "5f1939239bd35429ac9cd78f_right_profile.png"
},
"__v": 42,
"createdAt": "2020-07-23T07:15:47.387Z",
"updatedAt": "2020-08-18T18:54:22.272Z",
}
Talent collection
[
{
"_id": "5f38efef179aca47a0089667",
"userId": "5f1939239bd35429ac9cd78f",
"level": "5",
"chars": {
"type": "Fresher",
},
"category": "5f19357b50bcf9158c6be572",
"media": [],
"createdAt": "2020-08-16T08:35:59.692Z",
"updatedAt": "2020-08-16T08:35:59.692Z",
"__v": 0
},
{
"_id": "5f3b7e6f7e322948ace30a2c",
"userId": "5f1939239bd35429ac9cd78f",
"level": "3",
"chars": {
"type": "Fresher",
},
"category": "5f19359250bcf9158c6be573",
"media": [
{
"adminApproved": 0,
"status": 0,
"_id": "5f3c22573065f84a48e04a14",
"file": "id=5f1939239bd35429ac9cd78f&dir=test&img=5f1939239bd35429ac9cd78f_image_undefined.jpeg",
"description": "test",
"fileType": "image",
"caption": "test file"
},
{
"adminApproved": 0,
"status": 0,
"_id": "5f3c2d7a8c7f8336b0bfced2",
"file": "id=5f1939239bd35429ac9cd78f&dir=test&img=5f1939239bd35429ac9cd78f_image_1.jpeg",
"description": "this is a demo poster for testing",
"fileType": "image",
"caption": "A Test Poster"
}
],
"createdAt": "2020-08-18T07:08:31.532Z",
"updatedAt": "2020-08-18T19:35:22.899Z",
"__v": 2
}
]
And the category in the above document is a separate one populated to this. the category collection as,
[
{
"_id": "5f19359250bcf9158c6be573",
"status": true,
"title": "Testing",
"description": "Application tester",
"code": "test",
"characteristics": [],
"createdAt": "2020-07-23T07:00:34.221Z",
"updatedAt": "2020-07-23T07:00:34.221Z",
"__v": 0
},
{
"status": true,
"_id": "5f29829a705b4e648c28bc88",
"title": "Designer",
"description": "UI UX Designer",
"code": "uiux",
"createdAt": "2020-08-04T15:45:30.125Z",
"updatedAt": "2020-08-04T15:45:30.125Z",
"__v": 0
},
{
"_id": "5f19357b50bcf9158c6be572",
"status": true,
"title": "programming",
"description": "Java programmer",
"code": "program",
"createdAt": "2020-07-23T07:00:11.137Z",
"updatedAt": "2020-07-23T07:00:11.137Z",
"__v": 0
}
]
So my filter terms will be;
{
categories: ["5f19359250bcf9158c6be573", "5f19357b50bcf9158c6be572"],
minAge: 18,
maxAge: 25,
minHeight: 5,
maxHeight: 6,
minWeight: 50,
maxWeight: 80,
complexion: "white",
gender: "male",
}
And the expected result will be a user have both the above talents and followed conditions,
{
users: { ..User details.. },
medias: { ...medias from the matching talents.. }
}
If there are two collections you need to join them either by primary key or _id with foriegn fields and you can use $lookup with $match to filter down.
Documentation
You need to use $lookup with pipeline,
$match you condition for category match
$lookup to join users collection
$match conditions for users collections fields
$match exclude documents that don't found matching users of criteria passed in conditions
db.talents.aggregate([
{
$match: {
category: { $in: ["5f19359250bcf9158c6be573", "5f19357b50bcf9158c6be572"] }
}
},
{
$lookup: {
from: "users",
as: "users",
let: { userId: "$userId" },
pipeline: [
{
$match: {
$expr: {
$and: [
{ $eq: ["$$userId", "$_id"] },
{ $eq: ["$gender", "Male"] },
{ $eq: ["$education", "Btech"] }
// ... add you other match criteria here
]
}
}
}
]
}
},
{ $match: { users: { $ne: [] } } }
])
Playground
I have 2 entities to merge: Customer and Feedback. Feedback contains an embedded array of upvotes (Upvote)
A customer is not able to upvote more than once for a specific feedback.
What I would like to achieve is - given a specific feedback id - get the complete list of customers with an additional virtual attribute that states whether he/she upvoted the given feedback.
Customer.aggregate(
[
{
$match: { company_id: new ObjectID(req.user.company_id) }
},
{
$lookup: {
from: 'feedbacks',
let: { 'c_id': '$_id' },
pipeline: [
{
$unwind: '$upvotes'
},
{
$match: { $expr: { $eq: ['$upvotes.customer_id._id', '$$c_id'] } }
}
],
as: 'upvotes'
}
}
],
function(err, customers) {
if (err) {
console.log(err);
res.status(400).send(err);
} else {
res.send({ customers });
}
}
);
To do that I have to look through the list of upvotes for that specific feedback and, then, join it with the customer table using the customer_id.
The above mentioned approach does not work. Any suggestion what I am doing wrong?
Sample data (Feedback)
{
"size": 0,
"points": 50,
"status": "open",
"potential": 0,
"real": 5000,
"_id": "5c3d033271ceb7edc37d156c",
"title": "Custom Invoice Templates",
"description": "Provide an editor to create custom invoices.",
"owner_id": {
"_id": "5c3b684f7cec8be977c2a465",
"email": "maurizio#acme.com"
},
"company_id": "5c3b684f7cec8be977c2a462",
"project_id": "5c3b68507cec8be977c2a468",
"upvotes": [
{
"_id": "5c3fa5b371ceb7edc37d159a",
"comments": "bbbb",
"priority": "should",
"customer_id": {
"size": 0,
"potential": 0,
"real": 5000,
"_id": "5c3b68507cec8be977c2a485",
"name": "Oyomia Ltd."
},
"owner_id": {
"_id": "5c3b684f7cec8be977c2a465",
"email": "maurizio#acme.com"
}
}
],
"updatedAt": "2019-01-16T21:44:19.215Z",
"createdAt": "2019-01-14T21:46:26.286Z",
"__v": 0
}
Sample data (Customer)
{
"size": 0,
"potential": 0,
"real": 5000,
"_id": "5c3b68507cec8be977c2a485",
"name": "Oyomia Ltd.",
"contact": {
"_id": "5c40f8de71ceb7edc37d15ab",
"name": "Nick Page",
"email": "np#oyoma.com"
},
"company_id": "5c3b684f7cec8be977c2a462",
"deals": [
{
"value": 5000,
"_id": "5c3b68507cec8be977c2a487",
"name": "Armour batch",
"status": "won",
"type": "non_recurring",
"updatedAt": "2019-01-13T16:33:20.870Z"
}
],
"__v": 0,
"updatedAt": "2019-01-17T21:51:26.877Z"
}
Here i like to explain my problem.
How can i write a mongoose query to retrieve every subdocument from JSON without passing parent_id.
[
{
"_id": "56a320003fe17cc7363dd0d7",
"name": "Leanna Jacobson",
"gender": "female",
"friends": [
{
"id": 0,
"name": "Riley Case"
},
{
"id": 1,
"name": "Herman Carter"
},
{
"id": 2,
"name": "Pacheco Woodard"
}
]
},
{
"_id": "56a3200001501cfa1ea2641d",
"name": "Juliana Bonner",
"gender": "female",
"friends": [
{
"id": 0,
"name": "Keller Woodward"
},
{
"id": 1,
"name": "Fern Knight"
},
{
"id": 2,
"name": "Cain Richards"
}
]
},
{
"_id": "56a3200006864c78ecb1aeed",
"name": "Gena Stark",
"gender": "female",
"friends": [
{
"id": 0,
"name": "Kate Franco"
},
{
"id": 1,
"name": "Araceli Mcclure"
},
{
"id": 2,
"name": "Molly Nelson"
}
]
},
{
"_id": "56a320006d868155161038b6",
"name": "Eve Gonzalez",
"gender": "female",
"friends": [
{
"id": 0,
"name": "Pam Lang"
},
{
"id": 1,
"name": "Christy Marks"
},
{
"id": 2,
"name": "Donovan Warren"
}
]
},
{
"_id": "56a3200066b94852f5680568",
"name": "Coleman Wooten",
"gender": "male",
"friends": [
{
"id": 0,
"name": "Roberta Olson"
},
{
"id": 1,
"name": "Roseann Reid"
},
{
"id": 2,
"name": "Kerri Russell"
}
]
}
]
Here i need to retrieve every friends details from the subdocument array friends for every parent.
so how can i write query for this?????
Suppose the name of your schema is Person, try this one.
//find all document, only select `friends` field from every document
Person.find({}, 'friends', function (err, friends) {
// the return friends is the [[friends], [friends], ...]
});