Databases - MongoDB

About

  • MongoDB Atlas .

  • MongoDB Community Server .

    • It is asked if you want to install Compass during the installation.

  • MongoDB Compass .

  • Document-based, very flexible, good for large volumes of JSON data.

  • The local DB data is located in C:\Program Files\MongoDB\Server\8.0\data , but should be accessed via a connection, for security reasons.

  • Is it OOP?

    • Why MongoDB is not an OODBMS (Object-Oriented Database Management Systems):

      • MongoDB does not implement encapsulation, inheritance, or polymorphism, which are fundamental pillars of object-oriented databases (OODBMS). It does not store objects directly with associated methods and behaviors.

      • In MongoDB:

        • Data is stored as BSON documents (a binary version of JSON).

        • Documents represent objects with attributes (keys and values), but not behaviors (methods).

        • There is no native support for concepts like inheritance or direct references between objects.

    • In summary, it is OOP-like, but not OODBMS.

  • Documentation .

Export and Import

  • Can export in JSON or CSV.

  • Can import in JSON or CSV.

CLI

  • Tutorial using MongoDB Compass {Playlist with 21 videos (4 to 14)} .

    • The first 3 videos are unnecessary.

    • Videos 5 to 14 talk about CLI.

    • Videos 14 to 23 are about a ~primitive connection with Node.js and creation of an HTTP API.

    • Video 19 explains about Postman, to test HTTP calls.

    • Video 23 talks about "pagination", referring to the classic 'queries' of the URL.

  • mongosh

    • Enters the MongoDB Shell, if you are using an external shell.

  • help

    • Shows all MongoDB Shell commands, with explanations.

  • show dbs

    • Returns all dbs.

  • use bookstore

    • Changes to the bookstore db.

  • db

    • Returns the current db.

  • show collections

    • Returns all collections within the current db.

  • db.books

    • Returns the books collection, within the current db.

  • db.books.insertOne({titulo: "Cor da magia", autor: "Terry", rating: 9})

    • Adds a new document within the Books collection of the current db.

  • db.books.insertMany(_array_de_dict_)

    • Adds several new documents within the Books collection of the current db.

  • db.books.deleteOne(_filtro_)

    • Removes a document, identified by the filter.

    • Ideally, {_id: ObjectId("_numero_")}  is used, to ensure that the correct document is being deleted.

  • db.books.deleteMany({autor: "Terry"})

    • Deletes multiple documents, identified by the filter.

  • db.books.updateOne({_id: ObjectId(_numero_)}, {$set: {rating: 8, paginas: 200}})

    • Update Operators are used.

    • Updates the rating and the number of pages of the object identified by the ID.

  • db.books.updateMany({autor: "Terry"}, {$inc: {paginas: 5}})

    • Update Operators are used.

    • Increases the number of pages of the objects identified by the filter.

  • db.books.find(_filtro_opcional_)

    • A filter  can be passed as an optional parameter, as explained in the session below.

    • Within the Shell:

      • Returns the first 20 documents within the collection.

      • When typing it , the next 20 documents are displayed.

  • db.books.findOne(_filtro_)

    • Returns the first entry found, obtained by the filter.

  • db.books.find().count()

    • Returns a number with the amount of entries found by .find() .

  • db.books.find().limit(3)

    • Returns only 3 entries found by .find() .

  • db.books.find().sort({titulo: 1})

    • Format:

      • { entry: 1 or -1 }.

      • 1:

        • Ascending.

      • -1:

        • Descending.

    • Returns the entries found by .find() , sorted in Ascending order.

Query / Filters

  • In MongoDB Compass:

  • First argument: Filter

    • {rating: 9}

      • Only the documents where the rating is 9.

    • {genero: "magic"}

      • Returns the documents that contain the genre "magic" within the 'genre' array.

    • {genero: ["magic"]}

      • Returns the documents that contain ONLY the genre "magic" within the 'genre' array.

  • Second argument: Project

    • Format:

      • { entry: 1 or 0 }.

    • The '_id' always comes along, unless you use {id: 0}  in the second parameter.

    • {autor: "Terry"}, {titulo: 1}

      • Only the documents where the 'author' is Terry, displaying only the 'title' entries, with the _id.

    • {}, {titulo: 1, _id: 0}

      • All documents, displaying only the title of each document, without the _id.

Query Operators

  • List with all Query Operators .

  • **greater than:

    • db.books.find({rating: {$gt: 7}})

      • Returns all books with a rating greater than 7, without including 7.

  • **or:

    • db.books.find({$or: [{rating: 7}, {rating: 9}]})

      • Returns all books that have a rating equal to 7 or 9.

  • **in:

    • Super similar to or

    • db.books.find({rating: {$in: [7, 8, 9]}})

      • Returns all books that have a rating equal to 7, 8 or 9.

  • **not in:

    • db.books.find({rating: {$nin: [7, 8, 9]}})

      • Returns all books that have a rating different from 7, 8 or 9.

Update Operators

Schema without Mongoose

  • In MongoDB, schemas are not required because it is schema-less .

  • However, you can implement document validations through the JSON schema validation  feature. 

db.createCollection("users", {
  validator: {
    $jsonSchema: {
      bsonType: "object",
      required: ["name", "email", "password"],
      properties: {
        name: {
          bsonType: "string",
          description: "The user's name must be a string and is required."
        },
        email: {
          bsonType: "string",
          pattern: "^.+@.+\\..+$",
          description: "The email must be a valid string and is required."
        },
        password: {
          bsonType: "string",
          minLength: 6,
          description: "The password must be at least 6 characters long."
        },
        createdAt: {
          bsonType: "date",
          description: "Creation date, default is the current date."
        }
      }
    }
  }
});

Godot Driver