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

MongoDB - Quiz(MCQ)

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

A)

db.records.find( { â€œuser_idâ€: { $lt: 42 } }, { â€œhistoryâ€: 0 } )

B)

db.records.select( { â€œuser_idâ€: { $lt: 42 } }, { â€œhistoryâ€: 0 } )

C)

db.records.findOne( { â€œuser_idâ€: { $lt: 42 } }, { â€œhistoryâ€: 1 } )

D)

db.records.findOne( { â€œuser_idâ€: { $lt: 42 } }, { â€œhistoryâ€: 0 } )

Correct Answer : db.records.find( { â€œuser_idâ€: { $lt: 42 } }, { â€œhistoryâ€: 0 } )

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

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_______ disable balancing on a single collection in a sharded database.

A)

TagRange()

B)

sh._checkMongos()

C)

sh.removeTagRange()

D)

sh.disableBalancing()

Correct Answer : sh.disableBalancing()

Explanation : sh.disableBalancing() does not affect balancing of other collections in a sharded cluster.

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A)

sh.enableSharding()

B)

sh.enableBalancing()

C)

sh.getBalancerHost()

D)

All of the above

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A)

sh.enableBalancing()

B)

sh.getBalancerState()

C)

sh.getBalancerHost()

D)

None of the above

Correct Answer : sh.getBalancerState()

Explanation : sh.getBalancerState() returns true when the balancer is enabled and false if the balancer is disabled.

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