SQLite Interview Questions and Answers for 2 years experience

0
SQLite Interview Questions and Answers

  1. What is SQLite?

    • Answer: SQLite is a self-contained, serverless, embedded, relational database management system (RDBMS) that stores data in a single file. It's lightweight, easy to integrate, and doesn't require a separate server process.

  2. What are the advantages of using SQLite?

    • Answer: Advantages include its simplicity, ease of use, zero configuration, cross-platform compatibility, and its small footprint, making it ideal for embedded systems, mobile apps, and applications where a full-blown database server is overkill.

  3. What are the disadvantages of using SQLite?

    • Answer: Disadvantages include potential concurrency issues (though improved in recent versions), limited scalability compared to server-based databases, and a lack of advanced features found in larger RDBMS systems like Oracle or MySQL.

  4. Explain the difference between an INTEGER, REAL, and TEXT data type in SQLite.

    • Answer: INTEGER stores integers, REAL stores floating-point numbers, and TEXT stores text strings. SQLite offers flexible type affinity, meaning it attempts to interpret values based on their content, but explicitly defining the type is best practice.

  5. What is an SQL injection vulnerability, and how can you prevent it in SQLite?

    • Answer: SQL injection occurs when malicious SQL code is injected into database queries. In SQLite, this is prevented by using parameterized queries or prepared statements, which separate user input from the SQL code itself, preventing the injection of malicious commands.

  6. How do you create a new table in SQLite?

    • Answer: You use the `CREATE TABLE` statement. For example: `CREATE TABLE users (id INTEGER PRIMARY KEY, username TEXT, email TEXT);`

  7. How do you insert data into an SQLite table?

    • Answer: Use the `INSERT INTO` statement. For example: `INSERT INTO users (username, email) VALUES ('john.doe', 'john.doe@example.com');`

  8. How do you retrieve data from an SQLite table?

    • Answer: Use the `SELECT` statement. For example: `SELECT * FROM users;` or `SELECT username, email FROM users WHERE id = 1;`

  9. How do you update data in an SQLite table?

    • Answer: Use the `UPDATE` statement. For example: `UPDATE users SET email = 'new.email@example.com' WHERE id = 1;`

  10. How do you delete data from an SQLite table?

    • Answer: Use the `DELETE FROM` statement. For example: `DELETE FROM users WHERE id = 1;`

  11. Explain the concept of transactions in SQLite.

    • Answer: Transactions ensure atomicity, consistency, isolation, and durability (ACID properties) for database operations. They group multiple SQL statements together, so either all succeed or none do. They are controlled using `BEGIN TRANSACTION`, `COMMIT`, and `ROLLBACK`.

  12. What are indexes in SQLite, and why are they used?

    • Answer: Indexes are data structures that improve the speed of data retrieval from a database table. They work by creating a separate lookup table that points to rows in the main table, speeding up `SELECT` queries that use indexed columns. However, they add overhead to `INSERT`, `UPDATE`, and `DELETE` operations.

  13. How do you create an index in SQLite?

    • Answer: Use the `CREATE INDEX` statement. For example: `CREATE INDEX idx_username ON users (username);`

  14. What is a JOIN operation in SQL, and how is it used in SQLite?

    • Answer: A JOIN combines rows from two or more tables based on a related column. SQLite supports various JOIN types (INNER, LEFT, RIGHT, FULL OUTER) to retrieve data from multiple related tables.

  15. Explain the difference between INNER JOIN and LEFT JOIN.

    • Answer: An INNER JOIN returns only rows where the join condition is met in both tables. A LEFT JOIN returns all rows from the left table, even if there's no match in the right table (NULL values for unmatched columns in the right table).

  16. What is a primary key constraint, and why is it important?

    • Answer: A primary key uniquely identifies each row in a table. It ensures data integrity by preventing duplicate rows and providing a way to efficiently access specific rows.

  17. What is a foreign key constraint, and how does it relate to referential integrity?

    • Answer: A foreign key establishes a link between two tables, enforcing referential integrity. It ensures that values in a foreign key column in one table exist as primary keys in another table, preventing orphaned records.

  18. How do you handle NULL values in SQLite?

    • Answer: NULL represents the absence of a value. Use `IS NULL` or `IS NOT NULL` in WHERE clauses to check for NULL values. Functions like `IFNULL` can provide default values for NULLs.

  19. What are aggregate functions in SQLite, and give some examples?

    • Answer: Aggregate functions perform calculations on a set of values and return a single value. Examples include `COUNT`, `SUM`, `AVG`, `MIN`, `MAX`.

  20. How do you use the `GROUP BY` clause in SQLite?

    • Answer: The `GROUP BY` clause groups rows with the same values in specified columns, allowing aggregate functions to be applied to each group.

  21. How do you use the `HAVING` clause in SQLite?

    • Answer: The `HAVING` clause filters groups created by `GROUP BY`, based on conditions applied to aggregate functions.

  22. What is a subquery in SQLite, and how is it used?

    • Answer: A subquery is a query nested within another query. It's used to retrieve data that's used in the outer query's WHERE or FROM clause.

  23. How do you use the `LIKE` operator in SQLite?

    • Answer: The `LIKE` operator is used for pattern matching in strings, using wildcards `%` (matches any sequence of characters) and `_` (matches any single character).

  24. What are views in SQLite?

    • Answer: Views are stored queries that act like virtual tables. They don't store data themselves but provide a customized way to access data from underlying tables.

  25. How do you create a view in SQLite?

    • Answer: Use the `CREATE VIEW` statement, defining the view's name and the underlying query.

  26. How do you manage transactions to ensure data consistency?

    • Answer: Use `BEGIN TRANSACTION`, `COMMIT`, and `ROLLBACK` to manage transactions. Commit to save changes, rollback to undo them in case of errors.

  27. Describe your experience with optimizing SQLite queries for performance.

    • Answer: [Provide a detailed answer based on your own experience. Mention techniques like indexing, query rewriting, using appropriate data types, avoiding full table scans, and analyzing query execution plans.]

  28. How do you handle errors in SQLite applications?

    • Answer: [Explain your approach to error handling, mentioning exception handling mechanisms in your chosen programming language and how you've used them to gracefully handle database errors in SQLite applications.]

  29. Explain your experience working with SQLite in a specific project.

    • Answer: [Describe a relevant project, highlighting your role, the challenges you faced, and the solutions you implemented using SQLite. Quantify your achievements whenever possible.]

  30. How familiar are you with different SQLite libraries or tools for various programming languages?

    • Answer: [Mention specific libraries you've used, like the Python `sqlite3` module or similar libraries for other languages like Java, C++, etc.]

  31. What are some best practices for database design when using SQLite?

    • Answer: [Discuss normalization, proper data type selection, indexing strategies, efficient query design, and the importance of regular backups.]

  32. How would you approach troubleshooting a performance issue in an SQLite database?

    • Answer: [Outline a systematic approach, mentioning tools for analyzing query performance, checking indexes, identifying bottlenecks, and optimizing queries.]

  33. Have you worked with SQLite in a multi-threaded environment? If so, describe the challenges and how you addressed them.

    • Answer: [Discuss your experience with concurrency in SQLite, addressing potential issues like race conditions and deadlocks, and mentioning strategies like transactions or appropriate locking mechanisms.]

Thank you for reading our blog post on 'SQLite Interview Questions and Answers for 2 years experience'.We hope you found it informative and useful.Stay tuned for more insightful content!