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

If u want to retrieve the field "roll" only for all 10 records in the collections. Then try this.

In MongoDb :

db.students.find( { } , { " roll " : { " $roll " })

In Sql :

select roll from students