Free Practice Questions for the MongoDB Certified DBA Associate C100DBA Exam (2026 Updated)

Returns 5 comments, beginning with the last 10 items

Returns 10 comments, beginning with the last

Returns 10 comments, beginning with the first

Returns 5 comments, beginning with the first 10 items

Create

update

insert

delete

1024 bytes and 64 indexes

12 mega bytes and 64 indexes

64 bytes and 1024 indexes

1024 bytes and unlimited indexes

db.test.push({x:2,y: " apple " })

db.test.insert« " x " :2, " y " : " apple " })

db.test.insert({x:2,y: " apple " })

db.test.insert({x:2},{y: " apple " })

db.posts.find({author: " Tom " ».limit({tags:2})

db.posts.find({author: " Tom " ».limit($slice:{tags:2 > )

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.

db.posts.find({author: " Tom " > ,{tags:{$slice:2»)

mongotop

dbstats

mongostat

constats

db.collection.createlndex({relndex:l})

db.collection.reIndex({author:l})

db.collection.relndexQ

db.collection.createIndex({author:l}).reIndex()

db.sample.update( { " _id " : 3 } , { " $set " : { " _id " : 7 , " c " : 4 > > )

db.sample.update( { " _id " : 3 > , { " _id " : 7 , " c " : 4 > , { " justOne " : true > ) / □ This operation cannot be done with a single query.

db.sample.update( { " _id " : 3 > , { " _id " : 7 , " c " : 4 , { " $unset " : [ " a " , " b " ] } } )

db.sample.update( { " _id " : 3 > , { " _id " : 7 , " c " : 4 > )

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

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

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

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

No limit on document and 100 MB RAM

2 MB document and no limit on RAM

2 MB document and 100 MB RAM

16 MB document and 100 MB RAM

BSON

JSON

SOAP

XML

specify {all: true} as the third parameter of update command

updateAII instead of update

specify {updateAII: true} as the third parameter of update command

specify {multi : true} as the third parameter of update command

7

2

1

0

$aggregate

$sum

$match

$group

arbiter

hidden

primary

secondary

db.posts.find({ likes : { $gte : 100 , $lte : 200 } } );

db.posts.find({ likes : { $gt : 100 , $lte : 200 } } );

db.posts.find({ likes : { $gte : 100, $lt : 200 } } );

db.posts.find({ likes : { $gt : 100, $lt : 200 > > );

Number, Null, String and Object

Null, Number, Object and String

Null, Number, String and Object

String, Null, Number and Object

Skip and limit nullify each other. Hence returning the first five documents

Limits the first five documents and then return them in reverse order

Skips the first five documents and returns the sixth document five times

Skips the first five documents and returns the next five

Average of likes on all the posts of an author, grouped by author

Number of posts by an author

Sum of likes on all the posts by all the authors

Sum of likes on all the posts by an author, grouped by author

db.posts.createIndex({commerits.$.author " :-l});

db.posts.createIndex({comments.$.author " : {$desc:l > });

db.posts.createIndex({comments.author " :-l});

Perform queries against MongoDB collections

Perform administrative tasks

Use as a JavaScript framework for your production system

Fetches the posts with likes between 100 and 200 and sets their _id as null

Groups the posts by number of likes (101, 102, 103.) by adding 1 every time

Calculates the number of posts with likes between 100 and 200

Fetches the posts with likes between 100 and 200, sets the _id of the first document as null and then increments it 1 every time

mapReduce

group

aggregate

All of the above

255 K

1 MB

16 MB

2 MB

Multi-statement transactions

Joins

Authentication

2 MB

12 MB

There is no maximum size. It depends on the RAM.

16 MB

db.collection.showIndexes()

db.collection.findlndexes()

db.showIndexes()

db.collection.getlndexesQ

$project

$update

$modify

$set

A document will be inserted with the same _id as the last document inserted

A document that matches the collection ' s existing schema, but with null fields

A document with an _id assigned to be an Objectld

An empty document

No document will be inserted; an error will be raised

db.posts.find( { author: /John/ } )

db.posts.find( { author: /AjohnA/ > )

db.posts.find( { $like: {author: /John/} } )

db.posts.find( { author: {$like: /John/} } )

db.posts.find( { post_timestamp: { $fieldtype: null } } )

db.posts.find( { post_timestamp: { $type: null } } )

db.posts.find( { post_timestamp : { $type; 10 > > )

db.posts.find( { post_timestamp: { $fieldtype: 10 } } )

Two documents will be inserted with _id as 1

MongoDB will automatically increment the _id of the second document as 2

This will throw a duplicate key error

It will insert two documents and throw a warning to the user

$ elemMatch

$slice

Updating an array field without knowing its index is not possible.

$

{ _id : 3, quote : " Nobody will ever catch me. " }

{ _id : 1, quote : " That ' s a fact, Jack. " }

{ _id : 2, quote : " Find out if that fact is correct. " }

To help in disaster recovery

To protect agains network partitions

To enable certain read preference settings

To add greather redundancy

For more efficient backup operations