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

$set is used to set the value of a particular field in a document. The syntax of set is $set:{column_name : column_value}. Also, {multi:true} is needed to update all the documents. Otherwise only the first found document is updated.

Answer : C

Explanation

There is no direct way of changing the sharded key unless you dump the entire data, drop the sharded key and then re-import everything. Other all options are false. Sharding is enabled at collection level, it does not create any index by default and finally sharding environment supports regular sorting.

Q 3 - Consider that our posts collection contains an array field called tags that contains tags that the user enters.

{
            _id: 1,
            tags: [“tutorial”, “fun”, “learning”],
            post_text: “This is my first post”,	
            //other elements of document  	
} 

Which of the following commands will find all the posts that have been tagged as tutorial.

A - db.posts.find( { tags : "tutorial" } );

B - db.posts.find( { tags : ["tutorial"] } );

C - db.posts.find( { $array : {tags: "tutorial"} } );

D - db.posts.findInArray( { tags : "tutorial" } );

Answer : A

Explanation

Searching an array is no different than searching a normal field. Hence the first option.

Answer : A

Explanation

When you specify upsert: true for an update operation and no matching documents are found, MongoDB creates a new document.

Q 5 - Which of the following operator can be used to limit the number of documents in an array field of a document after an update is performed?

A - $push along with $each, $sort and $slice

B - $removeFromSet

C - $arrayLimit

D - None of the above

Answer : A

Explanation

You can iterate over all the array elements using $each, slice them using $slice and then push them back to the document using $push.

Answer : D

Explanation

There is no system collection to store database preferences.

Q 7 - In a sharded replica set environment, the w Option provides ability for write concern and j Option provides ability for the data to be written on disk journal. Consider that we have a seven member replica set and we want to assure that the writes are committed to journal as well as acknowledged by at least 3 nodes. What should be the value of w?

A - 0

B - 1

C - 3

D - 7

Answer : C

Explanation

The value of w determines the writes are committed and acknowledged by some minimum number of nodes which in this case is 3.

Answer : B

Explanation

The query in option 2, first of all groups the records by _id as author. This will group all the posts with same author and calculate the sum. Now that we have the sum with us, we are filtering on this count being greater than 1 in the next $match statement.

Q 9 - Which of the tags in a replica set configuration specify the operations to be read from the node with the least network latency?

A - primaryPreferred

B - secondaryPreferred

C - nearest

D - netLatency

Answer : C

Explanation

Operations read from member of the replica set with the least network latency, irrespective of the member’s type.

Q 10 - The ________ operator limits the contents of an array field from the query results to contain only the first element matching the query condition.

A - $

B - $elemMatch

C - $slice

D - An array cannot be retrieved element wise in MongoDB.

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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