MongoDB Online Quiz


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Following quiz provides Multiple Choice Questions (MCQs) related to MongoDB Framework. You will have to read all the given answers and click over the correct answer. If you are not sure about the answer then you can check the answer using Show Answer button. You can use Next Quiz button to check new set of questions in the quiz.

Questions and Answers

Answer : C

Explanation

The skip and limit functions are applies linearly and hence it will first skip documents 1-5, and then return documents 6-10.

Q 2 - What is the maximum size of a MongoDB document?

A - 2 MB

B - 16 MB

C - 12 MB

D - There is no maximum size. It depends on the RAM.

Answer : B

Explanation

The maximum BSON document size is 16 megabytes. The maximum document size helps ensure that a single document cannot use excessive amount of RAM or, during transmission, excessive amount of bandwidth.

Q 3 - Which of the following command can be used to check the size of a collection named posts?

A - db.posts.stats()

B - db.posts.findStats()

C - db.posts.find({stats:1})

D - db.stats({ collection : posts })

Answer : A

Explanation

To view the statistics for a collection, including the data size, use the db.collection.stats() method from the mongo shell.

Q 4 - Consider that the posts collection contains an array called ratings which contains ratings given to the post by various users in the following format:

{
         _id: 1,
         post_text: “This is my first post”,
         ratings: [5, 4, 2, 5],
         //other elements of document 			
}

Which of the following query will return all the documents where the array ratings contains at least one element between 3 and 6?

A - db.inventory.find( { ratings: { $elemMatch: { $gt: 3, $lt: 6 } } } )

B - db.inventory.find( { ratings: { ratings: { $gt: 5, $lt: 9 } } } )

C - db.inventory.find( { ratings: { ratings.$: { $gt: 5, $lt: 9 } } } )

D - db.inventory.find( { ratings: { $elemMatch: { $gte: 3, $lte: 6 } } } )

Answer : A

Explanation

$elemMatch operator is used to specify multiple criteria on the elements of an array such that at least one array element satisfies all the specified criteria.

Q 5 - Which option should be used with findAndModify() command to return the modified document instead of the pre-modification document?

A - findAndModify by default returns the pre-modification document

B - Set {new : true}

C - Use the POST version of findAndModify called findAndModifyPost

D - Both b and c are valid

Answer : B

Explanation

When true, returns the modified document rather than the original. The findAndModify() method ignores the new option for remove operations. The default is false.

Answer : D

Explanation

Capped collections are fixed-size collections that support high-throughput operations that insert and retrieve documents based on insertion order. Capped collections work in a way similar to circular buffers: once a collection fills its allocated space, it makes room for new documents by overwriting the oldest documents in the collection.

Q 7 - In a sharded replicas set environment with multiple mongos servers, which of the following would decide the mongos failover?

A - mongo shell

B - mongod

C - individual language drivers

D - mongos

Answer : C

Explanation

Since the mongos are itself failing in this case, this logic has to be built on the drivers side.

Answer : A

Explanation

MongoDB cannot create a unique index on the specified index field(s) if the collection already contains data that would violate the unique constraint for the index. The syntax for the same is db.collection.createIndex( { a: 1 }, { unique: true } )

Q 9 - Which of the following is the correct syntax for starting a new mongod process and specifying its replica set name as rs0:

A - mongod --replSet "rs0"

B - mongod --repl "rs0"

C - mongod "rs0"

D - First execute this: mongod --replSet. And then execute this: rs.add()

Answer : A

Explanation

Replica set can be set/stated using the –replSet command and specifying the replica name with it.

Q 10 - Which index is used to index the content stored in arrays?

A - Multikey Index

B - Compound Index

C - Text Index

D - Sparse Index

Answer : A

Explanation

MongoDB uses multikey indexes to index the content stored in arrays. If you index a field that holds an array value, MongoDB creates separate index entries for every element of the array.

mongodb_questions_answers.htm

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