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.
Q 1 - Which of the following is correct explanation of MongoDB processes?
A - mongod.exe is the shell process and mongo.exe is the actual database process
B - mongo.exe is the shell process and mongod.exe is the actual database process
C - mongos.exe is the MongoDB server process needed to run database
D - mongodump.exe can be used to import database backup dump
Answer : B
Explanation
The core components in the MongoDB package are: mongod, the core database process; mongos the controller and query router for sharded clusters; and mongo the interactive MongoDB Shell.
Q 2 - Which of the following commands finds all the documents in the posts collection with post timestamp field as null?
A - db.posts.find( { post_timestamp : { $type: 10 } } )
B - db.posts.find( { post_timestamp: { $type: null } } )
C - db.posts.find( { post_timestamp: { $fieldtype: 10 } } )
D - db.posts.find( { post_timestamp: { $fieldtype: null } } )
Answer : A
Explanation
$type is used for all the operations involving checking the type of a field in MongoDB. 10 represents the BSON value for null.
Q 3 - What does the following MongoDB command return?
db.posts.find( { likes : { $gt : 100 }, likes : { $lt : 200 } } );
A - Posts with likes greater than 100 but less than 200
B - Posts with likes greater than or equal to 100 but less than or equal to 200
Answer : C
Explanation
When the mongo shell interprets this query, it will override the first condition $gt and consider only the $lt one. To apply both the less than and greater than condition, you will have to use the $and operator.
Q 4 - What is the output of following two commands in MongoDB:
db.posts.insert({"_id":1})
db.posts.insert({"_id":1})
A - Two documents will be inserted with _id as 1
B - MongoDB will automatically increment the _id of the second document as 2
C - This will throw a duplicate key error
D - It will insert two documents and throw a warning to the user
Answer : C
Explanation
You cannot insert two documents with the same _id field. The value of _id field should be unique.
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?
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.
Q 6 - Which is the correct order (lowest to highest) in which MongoDB compares the BSON types?
A - Null, Number, String and Object
B - Number, Null, String and Object
Answer : A
Explanation
This is the defined order in which the bson types are compared. There are various other fields as per the BSON specification which can be found here: http://docs.mongodb.org/manual/reference/bson-types/
Answer : B
Explanation
The minimum number of sensible number of voting nodes is 3.
Q 8 - Which of the following commands create an unique index on author field of the posts collection?
A - db.posts.createIndex({"author":1 }, {"unique": true});
B - db.posts.createIndex({"author": unique });
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 tags in a replica set configuration specify the operations to be read from the node with the least network latency?
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.
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.
