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Question 16 Selectable Answer

Select all true statements about the differences between mongoexport and mongodump.

A. mongoexport outputs BSON file, but mongodump outputs JSON file.
B. mongoexport outputs JSON file, but mongodump outputs BSON file.
C. mongodump can create a data file and a metadata file, but mongoexport just creates a data file.
D. By default, mongodump sends output to stdout, but mongoexport writes to a file.
E. mongodump is typically faster than mongoexport

Answer:
Explanation:
https://docs.mongodb.com/database-tools/mongoexport/ https://docs.mongodb.com/database-tools/mongodump/

Question 17 Selectable Answer

Select all true statements about the update operation. (select 2)

A. updateOne() method with the $set operator updates the first document that matches the query.
B. If the field doesn't exist, updateOne() method with the $set operator will not add a new field with the specified value.
C. updateOne() method with the $set operator updates an existing document field with the given value.

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/method/db.collection.updateOne/

Question 18 Selectable Answer

Suppose you have a developers collection with the following document structure:
{
_id: 1,
fname: 'Bob',
lname: 'Smith',
tech_stack: [ 'git', 'c++', 'sqlite', 'linux' ]
}
Select a query that can be executed without errors.

A. db.developers.updateOne( { _id: 1 }, { $set: { _id: 3 } } )
B. db.developers.updateOne( { _id: 1 }, { $set: { fname: 'John' } } )
C. db.developers.updateOne( { _id: 1 }, { $unset: { _id: '' } } )
D. db.developers.updateOne( { _id: 1 }, { $set: { _id: 3, fname: 'Bob' } } )

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/method/db.collection.updateOne/

Question 19 Selectable Answer

How to display MongoDB configuration file from command line?

A. $ cat /var/mongod.conf
B. $ cat /etc/mongod.conf
C. $ cat /home/mongod.conf
D. $ cat /bin/mongod.conf

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/configuration-options/#use-the-configuration-file

Question 20 Selectable Answer

You have the following replica set configuration:
conf = {
"_id": "replset",
"version": 1,
"protocolVersion": 1,
"members": [
{
"_id": 0,
"host": "192.168.120.24:27017",
"priority": 2,
"votes": 1
},
{
"_id": 1,
"host": "192.168.120.24:27018",
"priority": 1,
"votes": 1
},
{
"_id": 1,
"host": "192.168.120.24:27019",
"priority": 1,
"votes": 1
}
]
}
Select all true statements about this configuration.

A. This configuration is incorrect. Host information must be unique for each member in a replica set.
B. This configuration is correct.
C. This configuration is incorrect. _id field must be unique for each member in a replica set.
D. This configuration is incorrect. You can only specify a priority of 0 or 1.

Answer:
Explanation:
https://docs.mongodb.com/manual/replication/#replication

Question 21 Selectable Answer

How to create a new user with the root role named root_user with password root123?

A. use admin db.createUser({ user: "root_user", pwd: "root123", roles: ["dbAdmin"] })
B. use admin db.createUser({ user: "root_user", pwd: "root123", roles: ["root"] })
C. use admin db.createUser({ user: "root_user", pwd: "root123", roles: ["clusterAdmin"] })
D. use admin db.createUser({ user: "root_user", pwd: "root123", roles: ["dbAdminAnyDatabase"] })

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/method/db.createUser/

Question 22 Selectable Answer

Given the following example document from an artists collection:
{
_id: 5,
last_name: 'Maurer',
first_name: 'Alfred',
year_born: 1868,
year_died: 1932,
nationality: 'USA'
}
and the following index:
db.artists.createIndex( { "last_name": 1, "nationality": 1 } )
How MongoDB will handle the query below?

A. db.artists.find( { "year_born": 1863 } )
B. None of these.
C. As a collection scan.
D. As an index scan.

Answer:
Explanation:
https://docs.mongodb.com/manual/indexes/

Question 23 Selectable Answer

Which of the following scenarios best suits the use of the Tree Pattern?

A. Product categories in the online store.
B. You want to store additional information about your products that are less used by your application.

Answer:
Explanation:
https://www.mongodb.com/blog/post/building-with-patterns-the-tree-pattern

Question 24 Selectable Answer

Which of the following commands can you use to exports data in BSON format from a MongoDB cluster?

A. mongodump
B. mongoexport
C. mongostore
D. mongoimport

Answer:
Explanation:
https://docs.mongodb.com/database-tools/mongodump/

Question 25 Selectable Answer

What is the best practice in using the $match operator?

A. The later in the pipeline, the better.
B. The earlier in the pipeline, the better. Not only because we will be using expression filters which reduce the number of documents to be processed, but also because we can use indexes.
C. It doesn't matter when we apply $match stage.

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/operator/aggregation/match/

Question 26 Selectable Answer

Select all true statements regarding to Aggregation Framework.

A. The Aggregation Framework will automatically reorder stages in a certain conditions (for optimization).
B. The query in a $match stage can not be entirely covered by an index.

Answer:
Explanation:
https://docs.mongodb.com/manual/aggregation/

Question 27 Selectable Answer

Select all true statements about indexes on a field with values of varying data types.

A. Values are ordered only by data type.
B. In MongoDB index cannot have different data types.
C. Values are ordered only by value.
D. Values are ordered by data type, then by value.

Answer:
Explanation:
https://docs.mongodb.com/manual/indexes/

Question 28 Selectable Answer

Select all true statements regarding to $out stage.

A. $out operator creates collections in the same database as the source collection.
B. All indexes on an existing collection are rebuilt when $out overwrites the collection.
C. $out operator must be the last stage in a pipeline.
D. $out operator will create a new empty collection or overwrite an existing collection if the pipeline raises an error.
E. $out operator will overwrite an existing collection if specified.

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/operator/aggregation/out/

Question 29 Selectable Answer

Which of the following actions are granted to the built-in read role?

A. find
B. remove
C. insert
D. update

Answer:
Explanation:
https://docs.mongodb.com/manual/reference/built-in-roles/#mongodb-authrole-read

Question 30 Selectable Answer

Why is high cardinality important when choosing a shard key?

A. Because documents with the same shard key will be placed in the same chunk. This can result in a very big chunk.
B. It's not important. Low cardinality is just as good as high cardinality.

Answer:
Explanation:
https://docs.mongodb.com/manual/core/sharding-shard-key/

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