MongoDB Online Quiz

Q 1 - Which of the following is incorrect statement about find and findOne operations in MongoDB?

A - find() returns all the documents in a collection while findOne() retrieves only the first one.

B - find() and findOne() returns cursors to the collection documents

C - findOne() returns the actual first document retrieved from a collection

D - find.limit(1) is not the same query as findOne()

Q 2 - What is the maximum size of Index Key Limit and Number of Indexes per collection?

A - 64 bytes and 1024 indexes

B - 12 mega bytes and 64 indexes

C - 1024 bytes and 64 indexes

D - 1024 bytes and unlimited indexes

Q 3 - Which of the following is the most important consideration while designing the schema for MongoDB?

A - The schema should match the data access and query patterns

B - The schema should be kept in 3NF similar to SQL schemas

C - The schema should focus on creating possible embedded documents

D - The schema should contain maximum indexes

Q 4 - Consider that you are using { upsert : true } option in your update command. Which of the following parameters will be used to determine if any new documents were inserted:

A - nMatched

B - nInserted

C - nModified

D - nUpserted

Q 5 - Which are the ONLY ways to project portions of an array?

A - $elemMatch

B - $slice

C - $

D - All 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 - Consider that you have a collection called population which has fields state and city. Which of the following query will calculate the population grouped by state and city?

A - db.population.aggregate( [{ $group: { _id: { state: "$state", city: "$city" },pop: { $sum: "$pop" } } }] )

B - db.population.aggregate( [{ $group: { _id: { state: "$state", city: "$city" },pop: { $sum: 1 } } }] )

C - db.population.aggregate( [{ $group: { _id: { state: "$state", city: "$city" },pop: { “$pop”: 1 } } }] )

D - db.population.aggregate( [{ $group: { _id: { city: "$city" },pop: { $sum: "$pop" } } }] )Multi Document Transaction is not supported by MongoDB

Q 8 - What is a replica set node which does not maintain its own data but exists only for voting purpose called?

A - Secondary

B - Arbiter

C - Delayed

D - Hidden

Q 9 - Consider that you have the following two documents in the products collection:

{ "_id" : 1, "prices" : [ 60, 100, 200 ] }

{ "_id" : 2, "prices" : [ 20, 90, 150 ] }

What will the following query result into:

db.products.update(
   { _id: 1, prices: 100 },
   { $set: { "prices.$" : 111 } }
)

A - Updates 60 to 100

B - Updates 100 to 111

C - Updates 60,100 and 200 to 111

D - Removes the three elements of the prices array and replaces it with only a single element 111

Q 10 - Consider the following document from the products collection:

{
 _id: 1,
 product_code: "345678",
 variations: [
              { size: "L", price: 1000 },
              { size: "M", price: 800 }
           ]
}

What does the following query using $elemMatch return?

db.products.find( { product_code: "345678" },
                 { variations: { $elemMatch: { size: “L” } } } )

A - Returns the complete document since MongoDB does not support partial array retrieval

B - Returns the document but with only one element in the variations array (corresponding to size L)

C - Returns the complete document but retrieves only the size field from the array

D - Returns the complete document but retrieves only the size field from the array and also with only one element in the variations array (corresponding to size L)