Deno Database Integration: PostgreSQL, MongoDB, and SQLite Essentials Quiz

Explore essential concepts of connecting Deno with PostgreSQL, MongoDB, and SQLite databases through this engaging quiz, designed to reinforce best practices and fundamental commands for database-driven application development. Strengthen your foundational knowledge of database operations with Deno using practical multiple-choice questions.

1. Deno PostgreSQL Connection Basics

   Which option correctly describes the main purpose of a connection pool when using Deno with a PostgreSQL database?

   1. It automatically backs up your PostgreSQL database daily.
   2. It encrypts all SQL queries sent to the database.
   3. It allows reuse of database connections to improve efficiency.
   4. It disables concurrent access to the database.

   Explanation: The connection pool in a database context manages and reuses open connections, reducing the overhead of establishing a new connection for every operation. This is crucial for performance and scalability. Automatic backups, query encryption, and disabling concurrent access are not the purposes of connection pools. Those distractors either misrepresent database features or refer to unrelated functionalities.

2. MongoDB Data Insertion with Deno

   If you want to add a new user object to a MongoDB collection using Deno, which type of database command should you use?

   1. insert
   2. connect
   3. update
   4. delete

   Explanation: Inserting documents is the standard operation to add new data in a NoSQL collection, and 'insert' is the relevant command. 'Update' changes existing data, 'delete' removes data, and 'connect' is only for making new database connections, not altering data.

3. SQLite File Location in Deno

   When initializing a SQLite database in Deno, which parameter do you typically provide to specify the data file location?

   1. A SQL SELECT statement
   2. A boolean flag for encoding
   3. A file path string
   4. A list of user credentials

   Explanation: The database requires a file path to know where to read/write the data file. SQL statements define database queries, encoding options are not used for file selection, and SQLite does not rely on user credential lists for local database file access.

4. Running a SELECT Query in PostgreSQL

   What is the primary use of a SELECT SQL statement when executing queries on PostgreSQL from Deno?

   1. Deleting a database
   2. Retrieving data from one or more tables
   3. Modifying server configuration
   4. Adding a new user account

   Explanation: A SELECT statement fetches data based on criteria, which is fundamental for read operations. Adding a user, deleting the database, and changing configuration all require different commands outside the scope of SELECT.

5. Storing Structured Data in MongoDB

   Which of the following describes the data structure most commonly stored in a MongoDB database when using Deno?

   1. Tab-delimited spreadsheets
   2. Fixed-length binary blobs
   3. Single raw text files
   4. JSON-like documents

   Explanation: MongoDB is designed to handle flexible, schema-less data organized as JSON-like documents. Storing raw text files, binary blobs, or tab-delimited spreadsheets is possible but not typical or directly supported as core data models.

6. Error Handling Best Practices

   Why is error handling important when querying databases such as PostgreSQL, MongoDB, or SQLite from a Deno application?

   1. It automatically optimizes all database queries.
   2. It permanently repairs broken data files.
   3. It helps catch issues like failed connections or invalid queries.
   4. It disables authentication requirements.

   Explanation: Error handling allows your application to respond gracefully to problems such as disconnections, malformed queries, or constraint violations. Query optimization, file repair, and overriding authentication are not functions of error handling and are misleading choices.

7. Prepared Statements Purpose

   What is the primary benefit of using prepared statements when working with SQL databases from Deno?

   1. Increasing screen display speed
   2. Reducing the risk of SQL injection attacks
   3. Replacing passwords with tokens
   4. Compressing database data files

   Explanation: Prepared statements separate SQL code from data, reducing the potential for malicious query manipulation. They do not compress files, affect the speed of user interfaces, or handle authentication token replacement.

8. Bulk Inserts in SQLite

   If you need to add multiple records efficiently to a SQLite database in Deno, which method is recommended?

   1. Writing all data to a CSV file only
   2. Running each insert in a separate connection
   3. Using a single transaction to batch inserts
   4. Restarting the database before every insert

   Explanation: Batching inserts within a single transaction minimizes overhead and is much faster. Separate connections for every insert are slow and resource-heavy. Writing to a CSV does not populate the database, and restarting the database is unnecessary and inefficient.

9. Database Drivers and Deno Permissions

   What Deno runtime permission typically needs to be granted to allow a database driver to access PostgreSQL, MongoDB, or SQLite databases?

   1. System clipboard read permission
   2. Direct browser control permission
   3. Network or file system access
   4. Camera usage permission

   Explanation: Interacting with databases requires either network access (for remote connections) or file system access (for local SQLite). Clipboard, camera, or browser permissions are unrelated to database communication.

10. Querying a Collection in MongoDB

    Which method is most commonly used in Deno to retrieve all documents from a MongoDB collection named 'products'?

    1. Issuing a DROP command
    2. Using the find method
    3. Calling deleteOne on the collection
    4. Invoking updateMany on the collection

    Explanation: The find method is designed for fetching documents that match specified criteria, including retrieving all items if no filter is applied. DeleteOne removes specific documents, updateMany alters existing records, and drop would remove the entire collection, not retrieve its contents.