Question

Which of the following query selects documents in the records collection that match the condition { “user_id”: { $lt: 42 } }?

(a) db.records.findOne( { “user_id”: { $lt: 42 } }, { “history”: 0 } )

(b) db.records.find( { “user_id”: { $lt: 42 } }, { “history”: 0 } )

(c) db.records.findOne( { “user_id”: { $lt: 42 } }, { “history”: 1 } )

(d) db.records.select( { “user_id”: { $lt: 42 } }, { “history”: 0 } )

The question was posed to me during an online interview.

The origin of the question is Read Operations in division MongoDB CRUD Concepts and Operation of MongoDB

Answer 1

Right answer is (b) db.records.find( { “user_id”: { $lt: 42 } }, { “history”: 0 } )

To elaborate: Query uses the projection { “history”: 0 } to exclude the history field from the documents in the result set.