MongoDB Aggregation Pipeline Fundamentals Quiz Quiz

Test your knowledge of MongoDB aggregation with these beginner-friendly questions covering the most common stages and concepts, including $match, $group, $project, $unwind, $lookup, and more. Ideal for interviews and revision on MongoDB’s data processing capabilities.

1. Understanding Aggregation Framework

   What role does the Aggregation Framework play in MongoDB when working with data?

   1. It is used for manual data entry.
   2. It only backs up data automatically.
   3. It deletes duplicated documents by default.
   4. It processes and transforms data using stages in a pipeline.

2. Identifying Aggregation Stages

   Which of the following is a stage that can be used to filter documents in an aggregation pipeline?

   1. $match
   2. $shape
   3. $insert
   4. $join

3. $group Stage Functionality

   When using the $group stage in MongoDB aggregation, what is the main result?

   1. Documents are converted into arrays.
   2. Documents are permanently deleted.
   3. Documents are randomly shuffled.
   4. Documents are grouped by a field and aggregate values like sum or count are calculated.

4. $project for Shaping Output

   How does the $project stage modify documents in a pipeline?

   1. By duplicating every document.
   2. By renaming the collection.
   3. By deleting odd-numbered documents.
   4. By including, excluding, or modifying specific fields in the output documents.

5. Deconstructing Arrays with $unwind

   If a document contains an items array, what does the $unwind stage do when applied?

   1. It encrypts the array values.
   2. It replaces arrays with numeric IDs.
   3. It merges all arrays into a single field.
   4. It creates separate documents for each element of the array.

6. Purpose of $lookup Stage

   What is the main purpose of the $lookup stage in a MongoDB aggregation pipeline?

   1. To perform a join between two collections and combine related data.
   2. To export data to an external CSV file.
   3. To change the data types of fields.
   4. To delete all duplicate documents.

7. Using $sort in Aggregation

   Which of the following describes the function of the $sort stage in an aggregation pipeline?

   1. It removes any empty arrays.
   2. It encrypts specific fields.
   3. It arranges documents in ascending or descending order.
   4. It splits arrays into separate fields.

8. Combining $match and $group

   What is an advantage of using $match before $group in a pipeline, for example filtering completed orders before aggregating totals?

   1. It automatically archives all documents.
   2. It skips the grouping altogether.
   3. It duplicates documents before grouping.
   4. It ensures only relevant documents are grouped and aggregated.

9. Understanding the $bucket Stage

   When using the $bucket stage in MongoDB aggregation, what happens to the documents?

   1. They are encrypted and hidden.
   2. They are grouped into defined ranges or 'buckets' based on a specific field's value.
   3. They are bookmarked for later use.
   4. They are converted into a CSV format.

10. Using $facet for Multiple Results

    What is the primary feature of the $facet stage in MongoDB aggregation?

    1. It allows multiple aggregation pipelines to run in parallel and returns multiple results.
    2. It splits documents into different databases.
    3. It deletes unused fields from every document.
    4. It compresses the output documents.