MongoDB C100DBA 問題集

質問 1：
Which option can be used with update command so that a new document gets created if no matching document is found based on the query condition?
A. {update: true, insert: true} as the third parameter of update command
B. This has to be handled in application code (Node.js, PHP, JAVA, C#, etc.) and cannot be handled in mongo shell query
C. Specify {upsert : true } as the third parameter of update command
D. upsert command instead of update command
正解：C

質問 2：
Consider the following posts document:

Which of the following queries will return the documents but with only the first two tags in the tags array?
A. db.posts.find({author:"Tom"}.limit({tags:2})
B. Both "db.posts.find({author:"Tom"},{tags:{$slice:2}})" and "db.posts.find({author:"Tom"}).limit($slice: {tags:2})" are valid. $slice works both with projection and limit.
C. db.posts.find({author:"Tom">,{tags:{$slice:2})
D. db.posts.find({author:"Tom"}.limit($slice:{tags:2})
正解：C

質問 3：
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. 3
B. 4
C. None of the above
D. 5
正解：B

質問 4：
'mongoimport' command is used for
A. Multiple command insertion
B. Batch data insertion
C. None of the above
D. Multiple command import
正解：B

質問 5：
Which of the following collections stores authentication credentials in MongoDB?
A. test.users
B. users.users
C. system.users
D. local.users
正解：C

質問 6：
The oplog (operations log) is a special capped collection that keeps a rolling record of all operations that modify the data stored in your databases. All the replica set members contain a copy of the oplog in the following collection:
A. <database>..oplog.rs
B. <replicasetid>.oplog.rs
C. local.oplog.rs
D. oplog.rs
正解：C

質問 7：
Which of the following is true about aggregation framework?
A. the aggregate command operates on a multiple collection
B. 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
正解：B,C,D

質問 8：
Which of the following commands will return all the posts with number of likes greater than 100 and less than 200, both inclusive?
A. db.posts.find({ likes : { $gte : 100 , $lte : 200 } } );
B. db.posts.find({ likes : { $gt : 100 , $lte : 200 } } );
C. db.posts.find({ likes : { $gt : 100, $lt : 200 > > );
D. db.posts.find({ likes : { $gte : 100, $lt : 200 } } );
正解：A