How to select a single field for all documents in a MongoDB collection?

Question

In my MongoDB, I have a student collection with 10 records having fields name and roll. One record of this collection is:

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Answer 1

While gowtham's answer is complete, it is worth noting that those commands may differ from on API to another (for those not using mongo's shell).
Please refer to documentation link for detailed info.

Nodejs, for instance, have a method called `projection that you would append to your find function in order to project.

Following the same example set, commands like the following can be used with Node:

db.student.find({}).project({roll:1})

SELECT _id, roll FROM student

Or
db.student.find({}).project({roll:1, _id: 0})

SELECT roll FROM student

and so on.

Again for nodejs users, do not forget (what you should already be familiar with if you used this API before) to use toArray in order to append your .then command.