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

This works for me,

db.student.find({},{"roll":1})

no condition in where clause i.e., inside first curly braces. inside next curly braces: list of projection field names to be needed in the result and 1 indicates particular field is the part of the query result