MongoDB Getting Started

In this lesson you get a MongoDB database running and send your first commands with the MongoDB Shell.

Two Ways to Get MongoDB

Option	What you do
MongoDB Atlas (cloud)	Sign up on the MongoDB website, create a free cluster, add a database user and allow your IP address. Nothing to install on your computer.
Local install	Download MongoDB Community Server for Windows, macOS or Linux, and install mongosh (the shell) and MongoDB Compass (a visual tool).

Atlas is the quickest start, and it is what most real apps use. When you add your IP address, you can choose "allow access from anywhere" while learning, but never leave that open for a real project.

Connect with mongosh

mongosh is the MongoDB Shell, a command line where you type JavaScript-style commands.

For a local server:

Example

bash

mongosh

For Atlas, copy the connection string from the Atlas "Connect" screen:

Example

bash

mongosh "mongodb+srv://cluster0.abcde.mongodb.net/" --username ayesha

The prompt shows the current database, such as test>.

Databases

Show all databases:

Example

javascript

show dbs

Output

admin   40.00 KiB
config  60.00 KiB
local   72.00 KiB

Switch to the institute database:

Example

javascript

use institute

Output

switched to db institute

The database does not really exist yet. MongoDB creates it automatically the moment you save the first document in it. That is why institute will not appear in show dbs until then.

The variable db always points to the current database:

Example

javascript

db

Output

institute

Collections

Like databases, collections are created automatically when you first insert into them:

Example

javascript

db.students.insertOne({ name: "Test Student", city: "Karachi" })

Output

{
  acknowledged: true,
  insertedId: ObjectId('6710a1f2c3b4d5e6f7a8b900')
}

Now both the database and the collection exist:

Example

javascript

show collections

Output

students

You can also create a collection yourself, which is useful for adding options later:

Example

javascript

db.createCollection("courses")

Output

{ ok: 1 }

Delete a Collection or Database

Example

javascript

db.students.drop()      // deletes the students collection
db.dropDatabase()       // deletes the current database

Both return true or { ok: 1, dropped: 'institute' } when they succeed. There is no undo, so double-check which database you are in first.

Useful Shell Commands

Command	What it does
`show dbs`	Lists databases
`use name`	Switches database (creates it on first insert)
`db`	Shows the current database
`show collections`	Lists collections in the current database
`db.createCollection("x")`	Creates a collection
`db.x.drop()`	Deletes a collection
`cls`	Clears the screen
`exit`	Leaves mongosh

MongoDB Compass

Compass is MongoDB's free desktop app. You paste the same connection string, then browse databases, edit documents and build queries with buttons. It also has the shell built in at the bottom of the window.

Exercise

You type use shop and nothing else. When does the shop database actually get created?

Immediately, when you type use shopWhen you insert the first document into a collection in itWhen you run show dbsNever, you must use db.createDatabase()