MongoDB Online Quiz

Q 1 - Which of the following MongoDB query is equivalent to the following SQL query:

UPDATE users SET status = "C" WHERE age > 25

A

db.users.update(
   { age: { $gt: 25 } },
   { status: "C" })

B

db.users.update(
 { age: { $gt: 25 } },
 { $set: { status: "C" } })

C

db.users.update(
 { age: { $gt: 25 } },
 { $set: { status: "C" } },
 { multi: true })

D

db.users.update(
 { age: { $gt: 25 } },
 { status: "C" },
 { multi: true })

Q 2 - Which of the following is true about sharding?

A - Sharding is enabled at the database level

B - Creating a sharded key automatically creates an index on the collection using that key

C - We cannot change a shard key directly/automatically once it is set up

D - A sharded environment does not support sorting functionality since the documents lie on various mongod instances

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" } );

Q 4 - Which option can be used with update command so that a new document gets created if no matching document is found based on the query condition?

A - Specify {upsert : true } as the third parameter of update command

B - upsert command instead of update command

C - {update: true, insert: true} as the third parameter of update command

D - This has to be handled in application code (Node.js, PHP, JAVA, C#, etc.) and cannot be handled in mongo shell query

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

Q 6 - Which of the following is not a system collection in MongoDB?

A - database.system.indexes

B - database.system.namespaces

C - admin.system.users

D - admin.system.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

Q 8 - What will be the equivalent MongoDB command for the following SQL command:

SELECT author, count(*) FROM posts GROUP BY author HAVING count(*) > 1

A

db.posts.aggregate( [
   {
     $group: {
        _id: "$author",
        count: { $sum: 1 },
		$match: { count: { $gt: 1 } }
     }
   }
] )

B -

db.posts.aggregate( [
   {
     $group: {
        _id: "$author",
        count: { $sum: 1 }
     }
   },
   { $match: { count: { $gt: 1 } } }
] )

C -

db.posts.aggregate( [
   { $match: { count: { $gt: 1 } } },
   {
     $group: {
        _id: "$author",
        count: { $sum: 1 }
     }
   }
] )

D -

db.posts.aggregate( [
   {
     $group: {
        _id: "$author",
        count: { $sum: "$author" }
     }
   },
   { $match: { count: { $gt: 1 } } }
] )

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

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.