CRUD Operations

Refer to the exhibit. What is the effect of the 'writeConcern' parameter in this operation?

What happens if you run an update operation with the $set operator on a field that does not yet exist in the document?

A retail application stores product documents in the `products` collection. Each document has an `inventory` array of embedded subdocuments, for example: `{ _id: 1, name: "Widget", inventory: [ { sku: "A1", qty: 5 }, { sku: "B2", qty: 8 } ] }`. The warehouse team needs to increase the `qty` of the subdocument with `sku: "B2"` by 3 for the product with `_id: 1`. Which update operation accomplishes this?

A developer needs to insert a document into the inventory collection and wants the operation to fail with a duplicate key error if a document with the same value for the sku field already exists. The sku field has a unique index. Which insert method and option combination achieves this with the least code?

Which operator is best used to add an element to an array only if it does not already exist?

A DBA is reviewing update operations that use the upsert option. Which TWO statements about upsert behavior in MongoDB are correct? (Choose two.)

A collection called events stores documents with an array field named tags. You need to remove all occurrences of the string "obsolete" from the tags array in every document where the array contains that value, without affecting other elements. Which update operator should you use?

When using the find() method, which cursor modifier is used to skip a specific number of documents before returning results?

What happens when you perform a find() query on a collection where the projection includes both an inclusion and an exclusion for different fields?

You are updating a document in the `products` collection. The document has an array field `tags`. You need to add the tag "sale" to the array only if it does not already exist, and you want to ensure that no duplicate tags are added even if multiple updates run concurrently. Which update operator should you use?

Refer to the exhibit. What is the impact of this operation on the document?

A DBA is reviewing a slow query on the `orders` collection. The query is: `db.orders.find( { status: "shipped", total: { $gt: 100 } } )`. The collection has an index on `{ status: 1, total: 1 }`. Which statement best describes how MongoDB will use this index to satisfy the query?

You are maintaining an inventory collection where each document has a field named `stock` (integer). A nightly job needs to atomically decrement `stock` by 1 for the document with `sku: "A100"` and also insert the current timestamp into a `lastUpdated` field in the same operation, without overwriting any other fields. Which update operation should you use?

Which method is the safest way to delete a single document from a collection based on a unique identifier?

Which THREE of the following are valid MongoDB CRUD query operators?

Which method is the most efficient way to perform a bulk update of multiple documents in a single request?

A developer needs to retrieve a subset of fields from a collection. Which TWO methods achieve this using projection?

What is the result of applying a $push operator with a value of [1, 2] to an existing array field [0]?

You are a MongoDB DBA at a retail company. The 'orders' collection has a document with _id: 100 and status: 'pending'. You need to atomically update the status to 'shipped' only if the current status is 'pending'. Which update operation should you use?

Refer to the exhibit. Which documents will this query return?

You are a MongoDB DBA and need to retrieve all documents from the 'products' collection where the 'price' field is greater than 100 and the 'category' is 'electronics'. Which query accomplishes this?

Which query operator matches documents where a field contains a value greater than or equal to a specified value?

Which operator is used to perform a logical OR operation across multiple query conditions?

What is the primary function of the 'projection' parameter in the find() method?

A sharded cluster stores customer documents in the customers collection, sharded on the customerId field. An application runs an updateOne with the filter { email: "user@example.com" } and the update { $set: { tier: "gold" } }. The email field is not the shard key and has no index. What is the most likely outcome of this operation?

A DBA is investigating a performance issue. A query on the `logs` collection uses the following filter: `{ $or: [ { level: "error" }, { level: "warning" } ] }`. There is an index on `{ level: 1 }`. Which statement correctly describes how MongoDB executes this query?

Which cursor method should you use to sort documents by a field named 'age' in descending order?

A MongoDB 6.0 replica set has a collection called orders with the default read concern. Users occasionally see an order document that still shows status "pending" even though a separate application thread just updated it to "shipped" and received an acknowledgment. The update used default write concern and targeted a single document by _id. Which read concern should you set on the read operation to guarantee the read returns data acknowledged by a majority of replica set members?

Which update operator would you use to increase the value of a numeric field by a specific amount?

You need to remove a single document from the `users` collection where the `email` field is "alice@example.com". The collection has a unique index on `email`. Which method should you use?

Which method should you use to update multiple documents in a collection and insert a new document if no matches are found?

When performing a findOne operation, what does MongoDB return if no document matches the query criteria?

Which operator would you use to remove an element from an array field in a document?