mongodb-quiz.md

MongoDB

Q1. Which command adds members to the replica set from MongoDB shell?

• rs.add("")
• replicaSetAdd("")
• rs.insert("")
• replica.add("")

Q2. Which MongoDB shell command should you use to back up a database?

• restore
• backup
• mongobackup
• mongodump

Q3. Which shell query displays all citizens with an age greater than or equal to 21?

• db.citizens.select('WHERE age >= 21')
• db.citizens.select('age >= 21')
• db.citizens.select('WHERE age >= 21')
• db.citizens.select({age: {$gte: 21}})

Q4. What does a MongoDB collection consist of?

• data
• documents
• fields
• rows

Q5. Given an ObjectId in _id, how do you get the time it was created?

• getDateTime(_id)
• _id.createDate()
• _id.getTimestamp()
• _id.getDateTime()

Q6. Given a cursor named myCursor, which command returns a boolean value?

• myCursor.hasNext()
• myCursor.sort()
• myCursor.next()
• myCursor.find()

Q7. Which command returns a specific document in the user's collection?

• db.users.find({_id: 1})
• db.users.seek({_id: 1})
• db.users.query({_id: 1})
• db.query.users({_id: 1})

Q8. To import a JSON array into Mongo, what flags are needed with MongoDBimport?

• --type jsonArray
• --json
• --type json
• --jsonArray

Q9. Choose the shell command that connects to a MongoDB database.

• mongo
• mongod
• mongoconnect
• dbconnect

Q10. In the MongoDB shell, how can you tell if an index was used with a query?

• db.customers.find({lastName: 'smith'}).explain()
• db.customers.find({lastName: 'smith'}).perf()
• db.customers.find({lastName: 'smith'}).plan()
• db.customers.find({lastName: 'smith'}).usedIndex()

Q11. Suppose your aggregation pipeline terminated with an exception referring to exceeded memory limit. What is the best way to resolve the issue?

• Set useMemory to twice amount indicated in exception.
• Switch a 64 bit instance of MongoDB.
• Increase the memory of the MongoDB server.
• Set allowDiskUse to true.

Q12. What is the recommended way to delete a user?

• db.deleteUser("user")
• db.removeUser("user") DEPRECATED
• db.remove("user")
• db.dropUser("user")

Q13. What the primary database in a replica set fails, when does failover begin?

• once the primary has been down for 10 minutes
• once the primary reboots
• immediately
• after the administrator reboots the primary

Q14. What is the correct option to set up Kerberos when starting MongoDBd?

• --setParameter authenticationMechanisms=GSSAPI
• --setAuthentication=GSSAPI
• --setParam auth=K
• --setAuth method=Kerberos

Q15. What is the purpose of an arbiter in a replica set?

• It monitors replica set and sends email in case of failure
• It casts the tie-breaking vote in an election.
• It holds a backup copy of the database.
• It reboots the failed server.

Q16. You would like to know how many types of items you have in each category. Which query does this?

• db.product.group({_id: "$category", count: {$sum:1}})
• db.product.aggregate($sum: {_id: "$category", count: {$group:1}}})
• db.product.aggregate($group: {_id: "$category", count: {$sum:1}}})
• db.product.aggregate($count: {_id: "$category", count: {$group:1}}})

Q17. To restrict the number of records coming back from a query, which command should you use?

• take
• limit
• max
• skip

Q18. We have a collection named restaurants with the geographical information stored in the location property, how do you create a geospatial index on it?

• db.restaurants.CreateIndex({location: "2dsphere"})
• db.restaurants.geospatial({location: "2dsphere"})
• db.restaurants.CreateIndex("2dsphere":"location")
• db.restaurants.CreateIndex({geospatial: "location"})

Q19. How do you find documents with a matching item in an embedded array?

• **db.customers.findmatch ({"jobs":"secretary"})**
• **db.customers.find ({"jobs:secretary"})**
• **db.customers.find ({"jobs":["secretary"]})**
• **db.customers.find ({"jobs":"secretary"})**

Q20. Which query bypasses the first 5 customers and returns the next 10?

• **db.customers.find({}, {skip: 5, limit: 10})**
• **db.customers.find({}.page(5).take(10))**
• **db.customers.find({}).skip(5).take(10)**
• **db.customers.find({}).skip(5).limit(10)**

Q21. How do you create a text index?

• db.customers.createIndex({firstName, lastName})
• db.customers.createTextIndex({firstName, lastName})
• db.customers.createIndex({firstName: "text", lastName: "text"})
• db.customers.createText({firstName: 1, lastName: 1})

Q22. Assuming you have customers collection with a firstName and lastName field, which is the correct MongoDB shell command to create an index on lastName, then firstName both ascending?

• db.customers.createIndex("lastName, firstName, ASC")
• db.customers.addIndex({lastName:"ASC", firstName: "ASC"})
• db.customers.newIndex({lastName:1, firstName:1})
• db.customers.createIndex({lastName:1, firstName: 1})

Q23. One of the documents in your collection has an _ id based upon an older database design and you want to change it. You write an update command to find the document and replace the _ id but the _ id isnt changed. How should you fix the issue?

• Set the replace option to true.
• Use the replaceOne() command instead.
• You cant. Once set the _ id field cannot be changed.
• Use the updateOne() command instead.

Q24. A compound index allows you to ___ ?

• Calculate interest quickly.
• Accomplish nothing, since compound indexes arent allowed in Mongo.
• Use more than one field per index.
• Combine fields in different collations.

Q25. Why are ad-hoc queries useful?

• They do not have to use the same operators.
• You do not need to structure the database to support them.
• They autogenerate reports.
• They run faster than indexed queries.

Q26. How often do the members of a replica set send heartbeats to each other?

• every 2 minutes
• every 5 seconds
• every 2 seconds
• every 10 seconds

Q27. Which command returns all of the documents in the customers collection?

• **db.customers.all()**
• **db.find().customers();**
• **db.customers.find();**
• **db.customers.show()**

Q28. Given a cursor named myCursor, pointing to the customers collection, how to you get basic info about it?

• myCursor.stats()
• myCursor.dump()
• myCursor.info()
• myCursor.explain()

Q29. What is true about indexes?

• They speed up read access while slowing down writes.
• They secure the database from intruders.
• They speed up reads and writes.
• They speed up write access while slowing down reads.

Q30. What is the preferred format to store geospatial data in MongoDB?

• Latitude, longitude
• XML
• GeoJSON
• BSON

Q31. Which programming language is used to write MongoDB queries?

• Python
• JavaScript
• SQL
• TypeScript

Q32. You have two text fields in your document and you'd like both to be quickly searchable. What should you do?

• Create a text index on each field.
• MongoDB is not able to do this.
• Create a compound text index using both fields.
• Create a text index on one field and a single field index on the other.

Q33. To import a CSV file into MongoDB, which command should you issue?

• mongorestore
• mongoi
• upload
• mongoimport

Q34. In an MongoDB mapReduce command, the reduce function should ____.

• access the database
• be called only when the key has a single value
• acces the database only to perform read operations
• not access the data

Q35. On a newly created collection, which field will have an index?

• the name field
• the Objectid field
• the _id field
• no field will have an index

Q36. You have a collection of thousands of students. You'd like to return the second set of 20 documents from the sorted collection. What is the proper order in which to apply the operations?

• limit, skip, sort
• sort, limit, skip
• limit, sort, skip
• sort, skip, limit

Q37. You would like the stats() command to return kilobytes instead of bytes. Which command should you run?

• db.vehicle.stats(1024)
• db.vehicle.stats("kilobytes")
• db.vehicle.stats(true)
• db.vehicle.stats("kb")

Q38. You'd like to modify an existing index. What is the best way to do this?

• Use the reIndex() command to modify the index.
• Delete the original index and create a new index.
• Call the createIndex() command with the update option.
• Use the updateIndex() command.

Q39. You need to delete the index you created on the description field. Which command will accomplish this?

• db.vehicle.dropIndex("description_text")
• db.vehicle.dropIndex({"description":"text"})
• db.vehicle.removeIndex({"description":"text"})
• db.vehicle.removeIndex("description_text")

Q40. You would like to know how many different categories you have. Which query will best get the job done?

• db.vehicle.distinct("category")
• db.vehicle.unique("category")
• db.vehicle.distinct("category").count()
• db.vehicle.distinct("category").length

Q41. From the MongoDB shell, how do you create a new document in the customers collection?

• **db.customers.add({name: "Bob"})**
• **db.customers.save({name: "Bob"})**
• **db.customers.create({name: "Bob"})**
• **db.customers.new({name: "Bob"})**

Q42. Which field is required of all MongoDB documents?

• _id
• _name
• objectId
• mongoDB is schema-less so no field is required

Q43. Which MongoDB shell command should you use to back up a database?

• backup
• restore
• mongobackup
• mongodump

Q44. Which shell query displays all citizens with an age greater than or equal to 21?

• **db.citizens.find('WHERE age >= 21')**
• **db.citizens.find({age: {\$gte: 21}})**
• **db.citizens.where('age >= 21')**
• **dbcitizens.select('WHERE age >=21')**

Q45. A MongoDB instance has at least what three files?

• data, namespcae, and journal
• namespace, journal, and log
• journal, data, and database
• data, log, and journal

Q46. You'd like a set of documents to be returned in last name, ascending order. Which query will accomplish this?

• db.persons.find().sort({lastName: -1}}
• db.persons.find().sort({lastName: 1}}
• db.persons.find().sort({lastName: ascending}}
• db.persons.find().sort({lastName: $asc}}

Q47. What is NOT a standard role in MongoDB?

• restore
• read/write
• dbadmin
• delete collections

Q48. Which command returns all of the documents in the customers collection?

• db.customers.show();
• db.customers.all();
• db.customers.find();
• db.find().customers();

Q49. Whih MongoDB shell command deletes a single document?

• db.customers.delete({_id: 1});
• db.customers.drop({_id: 1});
• db.drop.customers({_id: 1});
• db.customers.remove({_id: 1});

Q50. Using the MongoDB shell, how do you remove the customer collection and its indexes?

• db.customers.remove({}).indexes();
• db.customers.remove({});
• db.customers.drop();
• db.customers.delete();

Q51. By default, applications direct their read operations to which member of the replica set?

• primary
• arbiter
• secondary
• backup

Q52. You need to get the names of all the indexes on your current collection. What is the best way to accomplish this?

• db.people.getName();
• db.people.reIndex({names: 1});
• db.people.getIndexKeys();
• db.people.getIndex();

Q52. You are going to do a series of updates to multiple records. You find setting the multi option of the update() command too tiresome. What should you do instead?

• Use the replaceMany() command instead
• Use the updateMulti() command instead
• Use the updateMany command instead
• Set the global multi option to True

Q53. To cleanly shut down MongoDB, what command should you use from the MongoDB shell?

• quit()
• exit()
• db.shutdownServer()
• db.shutdown()

Q54. Given a customer collection which includes fields for gender and city, which aggregate pipeline shows the number of female customers in each city?

• db.members.aggregate([ {$match: {gender: "Female"}}, {$group: {_id: {city: "$city"}, number: {$sum: 1}}}, {$sort :{number: -1}}])
• db.members.find({$match: {gender: "Female"}}, {$group: {\_id: {city: "$city"}, number: {$sum: 1}}}.$sort ({number: -1})
• db.members.find([ {$match: {gender: "Female"}}, {$group: {_id: {city: "$city"}, number: {$sum: 1}}}, {$sort :{number: -1}}])
• db.members.aggregate([ {$match: {gender: "Female"}}, {$sort :{number: -1}}])