Creating A Database Using The Mongo Shell
If you connect to your Atlas cluster using the mongo shell and the connection string from the Atlas dashboard, you will automatically be connected to a database called test . If you immediately execute db.colors.insert({name:'red'}) then you will have just created a collection called colors in the database called test .
Don't want to use the test database? No problem - you can create a new database with the use command, like so:
use food
db.vegetables.insert({name: 'broccoli'})
.... will create a new database called food. The insert command shown will create a collection called vegetables.
Creating A Database From Your Application
If you click on the Connect button from the Clusters dashboard and select the URI Connection String, you'll see something like this:
mongodb://exampleuser:<PASSWORD>@server1:27017,server2:27017,server3:27017/<DATABASE>?ssl=true&replicaSet=example-shard-0&authSource=admin
New users sometimes wonder, "What name am I supposed to put in the <DATABASE> field?" or "How do I create the database that I will put in this string?". The answer is: just put any name you prefer - if the database does not yet exist, MongoDB will automatically create it.