MongoDB C100DBA Online Practice Questions and Exam Preparation

MongoDB C100DBA Online Questions & Answers

• Question 41:

  Which of the following operator can be used to control the number of items of an array that a query returns?

  A. $ elemMatch
  B. $slice
  C. $
  D. MongoDB does not support partial retrieval of items from an array
  B. $slice

• Question 42:

  Which of the following is true about aggregation framework?

  A. Each aggregation operator need to return atleast one of more documents as a result
  B. the aggregate command operates on a multiple collection
  C. A single aggregation framework operator can be used more than once in a query
  D. Pipeline expressions are stateless except accumulator expressions used with $group operator
  A. Each aggregation operator need to return atleast one of more documents as a result
  C. A single aggregation framework operator can be used more than once in a query
  D. Pipeline expressions are stateless except accumulator expressions used with $group operator

• Question 43:

  What is the use of mongodump and mongorestore tools?

  A. backup mongodb deployment
  B. audit mongodb deployment
  C. performance tune mongodb deployment
  D. replicate mongodb deployments
  A. backup mongodb deployment

• Question 44:

  What is the replication factor for a replicated cluster with 1 primary, 3 secondaries with one of them hidden. The set also has an arbiter?

  A. None of the above
  B. 5
  C. 3
  D. 4
  D. 4

• Question 45:

  Aggregation Pipelines have a limit of:

  A. No limit on document and 100 MB RAM
  B. 2 MB document and no limit on RAM
  C. 2 MB document and 100 MB RAM
  D. 16 MB document and 100 MB RAM
  D. 16 MB document and 100 MB RAM

• Question 46:

  Which of the following is correct about MongoDB?

  A. MongoDB supports geospatial indexes
  B. MongoDB supports some of the SQL functions
  C. MongoDB uses JSON format to represent documents
  D. MongoDB supports collection joins
  A. MongoDB supports geospatial indexes

• Question 47:

  Consider the following example document from the sample collection. All documents in this collection have the same schema.

  

  Which of the following queries will replace this with the document.

  

  A. db.sample.update( { "_id" : 3 } , { "$set" : { "_id" : 7 , "c" : 4 > > )
  B. db.sample.update( { "_id" : 3 > , { "_id" : 7 , "c" : 4 > , { "justOne" : true > ) / This operation cannot be done with a single query.
  C. db.sample.update( { "_id" : 3 > , { "_id" : 7 , "c" : 4 , { "$unset" : [ "a" , "b" ] } } )
  D. db.sample.update( { "_id" : 3 > , { "_id" : 7 , "c" : 4 > )
  C. db.sample.update( { "_id" : 3 > , { "_id" : 7 , "c" : 4 , { "$unset" : [ "a" , "b" ] } } )

• Question 48:

  Which command can be used to rebuild the indexes on a collection in MongoDB?

  A. db.collection.createlndex({relndex:l})
  B. db.collection.reIndex({author:l})
  C. db.collection.relndexQ
  D. db.collection.createIndex({author:l}).reIndex()
  C. db.collection.relndexQ

• Question 49:

  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.
  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

• Question 50:

  What does the output x of the following MongoDB aggregation query result into; db.posts.aggregate( [ { $group: { _id; "$author", x: { $sum: $likes } } } ] )

  A. Average of likes on all the posts of an author, grouped by author
  B. Number of posts by an author
  C. Sum of likes on all the posts by all the authors
  D. Sum of likes on all the posts by an author, grouped by author
  D. Sum of likes on all the posts by an author, grouped by author