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

In mongodb 3.4 we can use below logic, i am not sure about previous versions

select roll from student ==> db.student.find(!{}, {roll:1})

the above logic helps to define some columns (if they are less)