Free MongoDB C100DEV Exam Questions

Question 1

Consider the following documents in a MongoDB collection orders:

{

"_id": 1,

"customer_id": 101,

"item": "apple",

"price": 0.5,

"quantity": 100,

"date": ISODate("2022-01-01T00:00:00Z")

},

{

"_id": 2,

"customer_id": 102,

"item": "banana",

"price": 0.25,

"quantity": 50,

"date": ISODate("2022-01-02T00:00:00Z")

},

{

"_id": 3,

"customer_id": 101,

"item": "orange",

"price": 0.75,

"quantity": 75,

"date": ISODate("2022-01-03T00:00:00Z")

}

What is the aggregation pipeline to group the documents by "customer_id" and calculate the sum of the "quantity" field for each group, sorted in descending order by the sum of the "quantity" field?

A : db.runCommand({ aggregate: "orders", group: { _id: "$customer_id", total_quantity: { $sum: "$quantity" } }, sort: { total_quantity: -1 }})

B : db.orders.aggregate([ { $group: { _id: "$customer_id", total_quantity: { $sum: "$quantity" } } }, { $sort: { total_quantity: 1 } }])

C : db.orders.aggregate([ { $groupBy: { customer_id: "$customer_id" }, total_quantity: { $sum: "$quantity" } }, { $sort: { total_quantity: 1 } }])

D : db.orders.aggregate([ { $group: { _id: "$customer_id", total_quantity: { $sum: "$quantity" } } }, { $sort: { total_quantity: -1 } }])

Answer: D

Question 2

You are managing a MongoDB collection named orders, where each document represents an order. The documents contain the following fields:order_id (String): The unique identifier for the order.customer_name (String): The name of the customer who placed the order.total_amount (Number): The total amount of the order.status (String): The status of the order, which can be "pending," "shipped," or "delivered."items (Array of Strings): A list of items included in the order.You want to find all orders that meet the following criteria:The order has a total amount greater than $1000.The order status is either "pending" or "shipped."The order contains either "laptop" or "smartphone" in the list of items.Which of the following queries would return the correct documents?

A :

B :

C :

D :

Answer: D

Question 3

Consider a tasks collection that holds task records. The document structure is as follows:

{

"_id": ObjectId("64b64c58ed01c0a5e72dbf5f"),

"task": "Review PR",

"status": "pending",

"assignedTo": "alice"

}

Two operations are performed concurrently:

Operation A:

db.tasks.findAndModify({

query: { task: "Review PR", status: "pending" },

remove: true

});

Operation B:

db.tasks.findAndModify({

query: { task: "Review PR", status: "pending" },

update: { $set: { status: "completed" } },

new: true

});

Operation B starts slightly after Operation A but before Operation A completes. What will be the final state of the tasks collection after both operations have been executed?

A : The document will be removed from the collection.

B : The document's status will be updated to "completed".

C : A new document with the status "completed" will be inserted.

D : The document's status will remain "pending".

Answer: A

Question 4

Which of the following command skips the first 10 documents in the movies collection and returns all remaining documents?

A : db.movies.find().limit(10)

B : db.movies.find().sort(10)

C : db.movies.find().skip(5)

D : db.movies.find().skip(10)

Answer: D

Question 5

You manage a MongoDB collection called inventory that stores documents for a store's inventory. Each document has the fields item, category, and quantity. You want to ensure that an item is always present in the collection, even if it needs to be inserted. Specifically, if the item "notebook" in the "Stationery" category does not exist, it should be inserted with a quantity of 50. If it does exist, its quantity should be updated to 50. You plan to use the following command:

db.inventory.updateOne(

{ "item": "notebook", "category": "Stationery" },

{ $set: { "quantity": 50 } },

{ upsert: true }

)

What will happen after executing this command if there is no "notebook" item in the "Stationery" category in the inventory collection?

A : A new document will be inserted with only quantity: 50, as other fields (item and category) are not mentioned in the $set operator.

B : Nothing will happen because the $set operator only updates existing documents and cannot insert new ones.

C : A new document will be inserted with quantity: 50, but the item field will be set to null.

D : A new document will be inserted with item: "notebook", category: "Stationery", and quantity: 50.

Answer: D