CODEWITHSUNDEEP
mongodbmongooseaggregation-frameworkdata-modeling
Loki
Loki

Reputation: 1205

MongoDB design model for category and subcategory

Hi guys Im having a problem with MongoDB, I do not know how to design DB to support categories & subcategories...

So Im trying to create a Quiz app, with 2 models:

Question model

Category model

This is what Im trying to accomplish, I want to build Quiz app, the Quiz app will have 3 main categories: A category, B category and C category ...

Note: I will not have more than 20 subcategories per category

And each of the categories will have their own SubCategories like this: 'A category' will contains Test1, Test2, Test3, Test4, Test5... same for 'B category' it will contain Test1, Test2, Test3, Test4....

Note: I will not have more than 3 main categories

And each of this Test1, Test2 subcategories will contain a list of questions

So I based my model like this:

Category model:

export const CategorySchema = new mongoose.Schema({
  parent: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Category"
  },
  name: { type:String, required:true },
  slug: String,
});

Question Model:

export const QuestionSchema = new mongoose.Schema({
  question: { type:String, required:true },
  options: [String],
  answers: Array,
  category: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Category"
  }
});

With one additional catch, is that I would like a Question to be a part of different SubCategories, like it can be a part of A category > Test 1, B category > Test 2, A category > Test 3, so I can reuse it between different sub categories

My question is: Is this right way to design database ? Or is there some other way

Upvotes: 0

Views: 1708

Answers (1)

prasad_
prasad_

Reputation: 14287

I am using the reference that the Category and a Test together forms a tests collection, and the second collection is the questions. There are two models I can think of, and the choice is based upon your query and application needs.

Model 1:

tests:
    id: "A-Test1"
    category: "A",
    test: "Test1",
    name / description: "...",
    questions: [ "q1", "q2", "q15", "q16", "q25", ... ]

questions:
   id: "q1",
   details: { question: "...", options: [...], answer: [...] }

You want to find all questions for category "A" and "Test2":

  • Query on tests collection and get the questions.
  • Get question details from the questions collection; this would be a "join" query, using the aggregation stage $lookup.

You want to know if a question belongs to what categories/tests:

  • Query the tests collection's questions array.
  • Lookup the questions collection for more details about the question.


Model 2:

tests:
    id: "A-Test1"
    category: "A",
    test: "Test1",
    name / description: "..."

questions:
   id: "q1",
   details: { question: "...", options: [...], answer: [...] },
   tests: [ "A-Test1", "A-Test5", "C-Test2", ... ]

You want to find all questions for "A" and "Test2":

  • Query the questions collection, on the tests array.
  • Lookup the tests collection for more details about the test.

You want to know a question belongs to what categories/tests:

  • Query the questions collection, on the tests array.
  • Lookup the tests collection for more details about each test.

Upvotes: 1

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