MongoDB MongoDB Certifications C100DBA Questions & Answers

• Question 41:

  Consider the following document: > db.c.find()

  { "_id" : 12, b : [ 3, 5, 7, 2, 1, -4, 3, 12 ] }

  Which of the following queries on the "c" collection will return only the first five elements of the array in the

  "b" field? E.g.,

  Document you want returned by your query: { "_id" : 12, "b" : [ 3, 5, 7, 2, 1 ] >

  A. db.c.find( { > , { b : { $slice : [ 0 , 5 ] } } )

  B. db.c.find( { b : [ 0 , 5 ] > )

  C. db.c.find( { > , { b : { $substr[ 0 , 5 ] > > )

  D. db.c.find( { > , { b : [ 0, 1, 2, 3, 4, 5 ] > )

  E. db.c.find( { > , { b : [ 0 , 5 ] > )

  Correct Answer: A

• Question 42:

  Which mongodb tools allow us to work with our data in a human readable format?

  A. mongodump

  B. mongostat

  C. mongoimport

  D. mongoexport

  Correct Answer: CD

• Question 43:

  Which format/standard is used by MongoDB internally to store documents?

  A. JSON

  B. BSON

  C. B+ Trees

  D. JSON - Extended

  Correct Answer: A

• Question 44:

  What is the defau size of a GridFS chunk?

  A. 255 K

  B. 1 MB

  C. 16 MB

  D. 2 MB

  Correct Answer: A

• Question 45:

  'mongoimport' command is used for A. Batch data insertion

  B. None of the above

  C. Multiple command import

  D. Multiple command insertion

  Correct Answer: A

• Question 46:

  The difference between $push and $addToSet is:

  A. $addToSet needs the fields to be already present while $push will work even if the field is not present

  B. $addToSet adds the item to the field only if it does not exist already; while $push pushes the item to the field irrespective of whether it was present or not

  C. $addToSet adds the item to the field only if the new item is of the same datatype

  D. There is no major difference between them. $addToSet is a deprecated version of $push.

  Correct Answer: B

• Question 47:

  Consider the following documents:

  

  You perform the following query;

  

  How many documents will be updated by the query?

  A. 0

  B. 1

  C. 2

  D. 3

  E. 5

  Correct Answer: B

• Question 48:

  Which of the following index would be optimum for the query?

  Select all valid. db.test.find( { a : 5, c : 2 }) A. db.test.ensurelndex( { c:l, a: 1})

  B. db.test.ensurelndex( { a : 1, c: 1, d: 1, b : 1})

  C. CH db.test.ensurelndex( { a :1, c:l})

  D. db.test.ensurelndex( { a: 1, b :1, c:l, d:l})

  Correct Answer: BC

• Question 49:

  What does the following query do when performed on the posts collection? db.posts.update({_id:l}, {Title:This is post with ID 1"})

  A. Syntax error

  B. Replaces the complete document with _id as 1 with the document specified in second parameter

  C. Updates the Title of the post

  D. Updating a document is possible only with $set

  Correct Answer: B

• Question 50:

  Suposse tou have the following collection with only 2 documents:

  

  If you run an aggregation query and use { $unwind: "$traits" } as the first stage, how many documents will be passed to the next stage of the aggregation pipeline?

  A. 3

  B. 5

  C. 4

  D. 2

  E. 1

  Correct Answer: B