MongoDB Online Quiz

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

Q 1 - The MongoDB explain() method does not support which of the following verbosity mode:

A - queryPlanner

B - executionStats

C - allPlansExecution

D - customExecutionStats

Answer : D

Explanation

The possible modes of explain() are: "queryPlanner", "executionStats", and "allPlansExecution".

Answer : C

Explanation

The mongoimport tool imports content from an Extended JSON, CSV, or TSV export created by mongoexport, or potentially, another third-party export tool.

Answer : C

Explanation

MongoDB does not support things like ACID Transactions or atomicity across collections or relationships like SQL.

Answer : B

Explanation

{multi:true} should be used for this purpose. By default, MongoDB will update only the first document.

Q 5 - Which of the following methods can be used on a cursor object?

A - cursor.next()

B - cursor.hasNext()

C - cursor.forEach()

D - All of the above

Answer : D

Explanation

All of the above methods can be used on a cursor object.

Q 6 - What is the equivalent command in MongoDB for the following SQL query?

SELECT * FROM posts WHERE author like "%john%"

A - db.posts.find( { author: /john/ } )

B - db.posts.find( { author: {$like: /john/} } )

C - db.posts.find( { $like: {author: /john/} } )

D - db.posts.find( { author: /^john^/ } )

Answer : A

Explanation

db.posts.find( { author: /john/ } )

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.

Q 8 - In a replica set, a ________ number of members ensures that the replica set is always able to select a primary.

A - Odd

B - Even

C - Depends on the application architecture

D - 2

Answer : A

Explanation

An odd number of members ensures that the replica set is always able to elect a primary. If you have an even number of members, add an arbiter to get an odd number.

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 - Consider the following document from the products collection:

{
 _id: 1,
 product_code: "345678",
 variations: [
              { size: "L", price: 1000 },
              { size: "M", price: 800 }
           ]
}

What does the following query using $elemMatch return? 

db.products.find( { product_code: "345678" },
                 { variations: { $elemMatch: { size: L } } } )

A - Returns the complete document since MongoDB does not support partial array retrieval

B - Returns the document but with only one element in the variations array (corresponding to size L)

C - Returns the complete document but retrieves only the size field from the array

D - Returns the complete document but retrieves only the size field from the array and also with only one element in the variations array (corresponding to size L)

Answer : B

Explanation

The $elemMatch operator limits the contents of an <array> field from the query results to contain only the first element matching the $elemMatch condition.

mongodb_questions_answers.htm
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