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MongoDB

How to perform CRUD operations and use relationships with MongoDB.

MongoDB Installation​

You can install the free community server here.

Older instructions on how to download and install MongoDB.

tip

When installing MongoDB, note where the data and log directory are located. Then add both bin folders to the "PATH" environment variable.

Download the shell separately here.

MongoDB CRUD​

MongoDB CRUD Docs

To start, open the mongo shell and start mongosh.

show dbs shows all databases and their storage.

use [newDBname] creates newDBname. Then inside databases you can create collections.

CREATE​

db.collection.insertOne() or .insertMany(), where you then pass the JS object with data. Note that "collection" is the database name.

READ​

show collections shows all collections in the database.

Queries look like db.collection.find(query, projection, options). Reference is here.

info

Operator details like query, projection, and update operators can be found here.

Examples:

// finds everything in "products" collection
db.products.find();
// finds everything where name filed matches "Pencil"
db.products.find({ name: "Pencil" });
// finds everything where the price is greater than 1
db.products.find({ price: { $gt: 1 } });
// finds product with _id of 1, and only returns the "name" field
db.products.find({ _id: 1 }, { name: 1 });

UPDATE​

Reference here.

db.collection.updateOne(filter, update, options) updates one, can also use .updateMany().

  • filter: same as read operations "query" - what you are searching for
    • can have modifiers
  • update: what you want to do on the item you fine
  • options: additional options

Example:

// adds "stock" field to item with _id of 1, and sets the value to 32
db.products.updateOne({ _id: 1 }, { $set: { stock: 32 } });

DELETE​

db.collection.deleteOne(filter) deletes one item with filter. There is also .deleteMany().

Examples:

// deletes all items in "products" collection
db.products.deleteMany();
// deletes the row with a name of "Pencil"
db.products.deleteOne({ name: "Pencil" });
// delete database as a whole
db.dropDatabase();
// delete collection in database
db.collection.drop();

MongoDB Relationships​

First type of relationship is pretty obvious - you just include documents within the document. Like if you had reviews for a product, each review is a document.

Documents are anything in curly braces {}.

Example:

db.products.insertOne({
  _id: 2,
  name: "Pencil",
  price: 0.8,
  stock: 12,
  reviews: [
    {
      authorName: "Bob",
      rating: 5,
      review: "Wow!",
    },
    {
      authorName: "Joe",
      rating: 1,
      review: "I can't believe you've done this.",
    },
  ],
});

You can also have another type of relationship that goes into a separate collection, using the _id field for instance.

MongoDB REGEX​

MongoDB and REGEX

REGEX details

MongoDB with Node.js​

There's a native driver, and a DOM model called "Mongoose". Mongoose is much more popular.

Native version docs

MongoDB GUI - Studio 3T​

Studio 3T is the most popular and up-to-date GUI for MongoDB.

I use it (free) personally and it's great.