Top 35 Database Testing Interview Questions and Answers

CTA

In this blog, we’ll embark on an exciting journey through the world of database testing interview questions. From fundamental concepts to advanced techniques, we’ll equip you with the knowledge and confidence to conquer any interview scenario. Our database experts curated thought-provoking questions, testing scenarios, and best practices, providing you with the tools to shine during your next interview.

Database testing interview questions are categorized into three parts:

1. Basic Database Testing Interview Questions and Answers for Freshers

2. Intermediate Database Testing Interview Questions

3. Advanced Database Testing Interview Questions for Experienced

Most Frequently Asked Database Testing Interview Questions

• What is database testing?
• What do you understand about data-driven testing?
• Mention some DML commands.
• What is SQL?
• Name some common types of database testing techniques.
• What are white box and black box testing?
• Explain the relationship between data validation and database testing.
• Name some common types of database testing techniques
• Discuss the role of data masking in database testing and data security.
• Explain the concept of database migration testing.

1. What is Database Testing?

Database testing is the process of examining the data stored in a database as well as assessing the functionality and components that control the database entities, such as tables, stored procedures, views, triggers, and functions. 

Database testing is a crucial quality assurance process that verifies the accuracy, integrity, and performance of a database system. It involves validating data retrieval, modification, and storage operations. For example, in a relational database, foreign key implementation ensures referential integrity by linking tables through a shared key, preventing inconsistent or orphaned data entries.

1. Data Validity Testing: This type of testing requires familiarity with SQL queries to retrieve and validate data from the database.
2. Data Integrity Testing: Testers evaluate data against imposed limitations and database integrity requirements to ensure data integrity.
3. Database Performance Testing: Testers assess the performance of triggers, indices, and processes to determine their efficiency. The system should be able to handle database transactions effectively. A solid understanding of database structures is necessary for this type of testing.
4. Validation of Logic: This involves verifying the logic associated with triggers, functions, and procedures present in the database.

2.What do you understand about data-driven testing?

Data-driven testing is a software testing methodology where test scenarios are executed using various external data sets. It aims to validate application functionality across multiple data inputs, enhancing test coverage and efficiency. For instance, in a database system, foreign key implementation ensures data integrity by linking a column in one table with the primary key of another table, preventing inconsistent or invalid data entries.

3. Mention some DML commands.

Data Manipulation Language (DML) commands are used to insert, update, delete, and select data from a database. The most common DML commands are as follows:

• SELECT: Retrieves data from a database.
  • Syntax: SELECT column1, column2 FROM table_name WHERE condition;
  • Example: SELECT student_name, score FROM exam_results WHERE score > 90;
• INSERT: Adds new records to a table.
  • Syntax: INSERT INTO table_name (column1, column2) VALUES (value1, value2);
  • Example: INSERT INTO employees (emp_id, emp_name) VALUES (101, ‘John Smith’);
• UPDATE: Modifies existing records.
  • Syntax: UPDATE table_name SET column1 = value1 WHERE condition;
  • Example: UPDATE products SET price = 25 WHERE product_id = 123;
• DELETE: Removes records from a table.
  • Syntax: DELETE FROM table_name WHERE condition;

Example: DELETE FROM customers WHERE customer_id = 456;

4. What is SQL?

Structured query language (SQL) is a standardized domain-specific language used for managing relational databases. Its primary purpose is to retrieve, manipulate, and manage data stored in relational database management systems (RDBMS). It was introduced in 1974 by IBM’s Donald D. Chamberlin and Raymond F. Boyce. SQL is now maintained by the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO).

5. Name some types of database testing techniques.

Here are the major types of database testing techniques:

• Structural Testing: This type of testing verifies the structure of the database, such as the tables, columns, and relationships.
• Functional Testing: Functional testing verifies the functionality of the database, such as the ability to insert, update, delete, and query data.
• Non-Functional Testing: It verifies the non-functional aspects of the database, such as performance, scalability, and security.
• Security Testing: This type of testing verifies the security of the database against unauthorized access, modification, or destruction of data.
• Recovery Testing: This type of testing technique verifies the ability of the database to recover from failures, such as hardware failures or software errors.

6. What are white box testing and black box testing?

White box testing is a method where internal code structures, logic, and algorithms are analyzed to identify errors. An example is reviewing the source code of a software application to find bugs. Black box testing evaluates the functionality of the software without inspecting its internal code; for instance, testing a website’s user interface by interacting with it without knowledge of the underlying code.

7. Explain the relationship between data validation and database testing.

Database testing and data validation are interrelated processes in software quality assurance. Database testing involves verifying the accuracy and reliability of data stored in a database, ensuring it conforms to defined rules and structures; for example, checking that a customer’s birthdate is within a valid range.

Data validation, on the other hand, focuses on input data before it enters the database, ensuring it meets predefined criteria; for instance, validating that an email address provided during registration follows the correct format. Both processes collectively ensure data integrity and consistency in software applications.

8. Name some common types of database testing techniques.

Common types of database testing techniques include data validity testing, data integrity testing, database performance testing, database security testing, database recovery testing, database migration testing, database scalability testing, database usability testing, stored procedure testing, and database integration testing.

9. Discuss the role of data masking in database testing and data security.

Data masking plays a pivotal role in both database testing and data security. It involves the encryption of sensitive data within databases, thereby ensuring confidentiality during testing processes. This practice makes sure that real data remains confidential, minimizing security risks. Also, data masking aids in compliance with data protection regulations and provides overall data security measures, assuring data integrity and trustworthiness in database environments.

10. Explain the concept of database migration testing.

migration testing involves validating the successful migration of data from one database system to another, ensuring data integrity and compatibility. It ensures that the data remains intact, accurately transferred, and usable in the target database.

11. Discuss the role of database triggers in maintaining data consistency and how they can be tested.

Database triggers play a crucial role in maintaining data consistency by automating actions when specific events occur, ensuring data integrity, and enforcing business rules. To test them, one can employ unit testing frameworks to verify trigger functionality, assessing responses to various input scenarios. Triggers can be tested using unit testing, integration testing, and system testing. For instance, consider a trigger that updates inventory levels when a sale is recorded in an e-commerce system, guaranteeing real-time accuracy in stock information.

12. Explain the concept of database partitioning and its relevance in testing.

Database partitioning is a technique that divides a database into smaller, more manageable pieces. This can be done for a variety of reasons, such as performance, scalability, or security.

In testing, database partitioning can be used for the following:

1. Improve Performance: By dividing the database into smaller pieces, queries can be executed more quickly. This is because the database server does not have to scan the entire database for each query.
2. Improve Scalability: By dividing the database into smaller modules, it can be scaled out to more servers. This can help handle increased traffic or workload.
3. Improve Security: By dividing the database into smaller pieces, it can be easier to control access to sensitive data.

13 Describe the concept of database normalization and its importance in testing.

Database normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It is a fundamental concept in database design and is important for both performance and testing.

There are three main levels of database normalization:

• First Normal Form (1NF): Thisis the most basic level of normalization and requires that each table in the database have a primary key. The primary key is a unique identifier for each row in the table.
• Second Normal Form (2NF): 2NF requires that each non-primary key column in a table be dependent on the primary key. This means that each column in the table must contain data that is unique to the row.
• Third Normal Form (3NF):This level of normalization requires that each non-primary key column in a table be independent of all other non-primary key columns. This means that each column in the table must contain data that is unique to the row and is not dependent on any other column in the table.
• Boyce-Codd Normal Form (BCNF)is a database normalization concept that ensures the elimination of partial dependencies in relational databases. It enforces stricter criteria for table design, preventing data redundancy and anomalies. BCNF is vital for maintaining data integrity and efficient query performance in relational database systems.

14. How do you test database triggers and procedures?

To assess database procedures and triggers, it is crucial to have knowledge of input and output parameters. The ‘EXEC’ statement facilitates the execution of procedures, allowing examination of table behaviors. Follow these steps:

• Open the database project in the Solution Explorer
• Access the database schema via the ‘View’ menu
• Navigate to the project folder from the schema view
• Right-click on the object requiring testing and select ‘Create Unit Tests’
• Create a new language test project
• Choose either a) Insert the unit test or b) Create a new test and click ‘OK’
• Configure the project using the Project Configuration dialog box
• Confirm the configuration and click ‘OK’ to proceed.

15. What are Acid Properties?

ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that a transaction is treated as a single, indivisible unit of work. Either all the operations within the transaction are completed successfully, or none of them are.
• Consistency ensures that the database remains in a consistent state before and after a transaction is executed.
• Isolation ensures that concurrent transactions do not interfere with each other.
• Durability ensures that the results of a transaction are not lost even if there is a system failure.

16. How is database testing different from front-end testing ?

Here are the differences between database testing and front-end testing:

17. Mention some database testing tools.

Below are the major database testing tools:

• DBUnit is a Java-based tool that helps with setting up test data and verifying database results. It can be used with a variety of databases, including MySQL, Oracle, and Microsoft SQL Server.
• Apache JMeter is an open-source tool that can be used for load testing, performance testing, and functional testing of databases. It can be used to simulate a large number of users accessing the database simultaneously.
• SQL Power Architect is a commercial tool that provides a graphical user interface for creating and managing test cases for databases. It also includes a number of features for automating the testing process.
• Toad for Oracle is a commercial tool that provides a comprehensive set of features for testing Oracle databases. It includes features for creating and managing test cases, executing test cases, and analyzing test results.
• TestComplete is a commercial tool that can be used for testing a variety of software applications, including databases. It includes features for creating and managing test cases, executing test cases, and analyzing test results.

18. Why are SQL constraints used in a database?

SQL constraints are essential in databases to maintain data integrity and enforce data quality standards. They ensure that data entered into tables sticks to predefined rules, preventing erroneous or inconsistent information. For instance, a ‘UNIQUE’ constraint ensures that a column contains only unique values, preventing duplicate entries and maintaining the accuracy of the database. This enhances data reliability and overall database performance.

There are many different types of SQL constraints, including:

• NOT NULL constraints: These constraints ensure that a column cannot contain a NULL value.
• UNIQUE constraints: These constraints ensure that each row in a table has a unique value in a particular column.
• CHECK constraints: These constraints allow you to specify a condition that the data in a column must meet.
• FOREIGN KEY constraints: These constraints ensure that the value in a column refers to a valid value in another table.

19. What are CRUD operations?

CRUD stands for Create, Read, Update, and Delete. These are the four basic operations that are performed on data in a database.

• Create is the operation of adding new data to the database.
• Read is the operation of retrieving data from the database.
• Update is the operation of modifying existing data in the database.
• Delete is the operation of removing data from the database.

20. What are joins, and what are the different types of joins?

Joins in database management are operations that combine data from multiple tables based on specified conditions. Different types of joins include:

1. INNER JOIN: Retrieves matching records from both tables.
   1. Syntax: SELECT * FROM tableone INNER JOIN tabletwoON column = tabletwo.column;
   2. Example: SELECT orders.order_id, customers.customer_name FROM orders INNER JOIN customers ON orders.customer_id = customers.customer_id;
2. LEFT JOIN (or LEFT OUTER JOIN): Retrieves allrecords from the left table and matching records from the right table.
   1. Syntax: SELECT * FROM tableone LEFT JOIN tabletwoON column = tabletwo.column;
   2. Example: SELECT employees.employee_id, departments.department_name FROM employees LEFT JOIN departments ON employees.department_id = departments.department_id;
3. RIGHT JOIN (or RIGHT OUTER JOIN): Retrieves all records from the right table and matching records from the left table.
   1. Syntax: SELECT * FROM tableone RIGHT JOIN tabletwoON column = tabletwo.column;
   2. Example: SELECT products.product_name, orders.order_date FROM products RIGHT JOIN orders ON products.product_id = orders.product_id;
4. FULL JOIN (or FULL OUTER JOIN): Retrievesall records when there is a match in either the left or right table.
   1. Syntax: SELECT * FROM tableone FULL JOIN tabletwoON column = tabletwo.column;
   2. Example: SELECT customers.customer_name, orders.order_id FROM customers FULL JOIN orders ON customers.customer_id = orders.customer_id;
5. SELF JOIN: Joins a table to itself;typically used to retrieve hierarchical data.
   1. Syntax: SELECT * FROM tableone t1, tableone t2 WHERE t1.column = t2.column;
   2. Example: SELECT e1.employee_name, e2.manager_name FROM employees e1, employees e2 WHERE e1.manager_id = e2.employee_id;

21. How can data anomalies such as duplicates, null values, or outliers be identified in database testing?

Data anomalies such as duplicates, null values, or outliers can be identified in database testing using a variety of methods, including:

1. Data Profiling:Data profiling is the process of collecting and analyzing data to understand its characteristics. This can be done using a variety of tools, such as database discovery tools, data quality tools, and data mining tools. Data profiling can be used to identify data anomalies by looking for data that is out of range, inconsistent, or missing.
2. Data Analysis: Data analysis involves examining, purifying, modifying, and shaping data to uncover valuable insights, inform conclusions, and aid in decision-making.Data analysis can be used to identify data anomalies by looking for data that does not fit the expected patterns.
3. Data Visualization:Data visualization is the process of transforming data into a visual format that can be easily understood. Data visualization can be used to identify data anomalies by looking for data that stands out from the rest.

22. What is meant by database schema validation, and how is it performed?

Database schema validation is the process of checking whether a database schema conforms to a set of rules. This can be done manually or automatically. Schema validation can be performed on a regular basis to help ensure the integrity of the database.

Here are some of the benefits of performing database schema validation:

1. Data Integrity: Schema validation can help ensure that the data in your database is accurate and consistent.
2. Performance: Schema validation can help improve the performance of your database by preventing errors that can slow down queries.
3. Security: Schema validation can help improve the security of your database by preventing unauthorized users from accessing or modifying data.

23. How can performance bottlenecks in database queries be identified and optimized?

Performance bottlenecks in database queries can be identified and optimized by using a variety of tools and techniques. Some of the most common methods include:

1. Query Profiling: This involves running a query and collecting statistics about its performance, such as the amount of time it takes to execute, the number of rows it returns, and the amount of memory it uses. This information can be used to identify the areas where the query performs poorly and to make changes to improve its performance.
2. Indexing: This involves creating indexes on tables to improve the performance of queries that access specific columns or ranges of data. Indexes can help speed up queries by reducing the amount of data that needs to be scanned.
3. Rewriting Queries: This involves changing the structure of a query to improve its performance. For example, a query that joins two tables can often be rewritten to use a single table, which can improve performance.

24. What do you mean by data redundancy?

Data redundancy refers to the storage of the same data in multiple places within a database or data storage system. This can occur accidentally but is also done deliberately for backup and recovery purposes.

Accidental data redundancy can happen when data is entered into multiple systems or databases without being properly synchronized. This can lead to inconsistencies and errors in the data, as well as making it difficult to keep track of changes.

Deliberate data redundancy is often used as a way to improve performance and availability. For example, a database may store a copy of its data on a backup server in case the primary server fails. This way, users can still access the data even if the primary server is unavailable.

25. Explain the importance of database migration testing.

Data Integrity: Database migration testing ensures that data is accurately and completely transferred without loss or corruption during the migration process. It validates the integrity of migrated data to maintain data consistency and reliability.

Compatibility: It verifies that the migrated data is compatible with the target database system, including the database schema, data types, constraints, and indexes. This helps avoid any compatibility issues that may arise during the migration.

Functionality: Database migration testing ensures that the functionality of the application or system relying on the migrated database remains intact. It verifies that all queries, stored procedures, triggers, and other database-related functionality work as expected in the new environment.

Performance: It assesses the performance of the migrated database by executing queries, transactions, and other operations to ensure that the performance is on par with or better than the original database.

Here are some frequently asked advanced database testing interview questions and answers:

26. What is the QTP testing process, and how do you use SQL queries in QTP?

QTP (QuickTest Professional) serves as a commercial automation testing tool employed to conduct functional testing on software applications. The QTP testing process typically encompasses these stages:

• Requirement Collection: Initially, the software application’s requirements are gathered.
• Test Case Formulation: After acquiring the requirements, test cases are crafted to validate the application’s functionality.
• Script Creation: The test cases are then developed within QTP, utilizing VBScript or Java.
• Data Arrangement: The necessary data for executing the test cases is prepared.
• Test Execution: Subsequently, the test cases are executed against the application.
• Reporting: Finally, the outcomes of the test execution are documented and reported.

27. Can Selenium be used for database testing?

Selenium can be used for database testing, but it is not a dedicated database testing tool. It can be used to automate queries and verify the results, but it cannot perform more complex database testing tasks such as data validation and security testing.

28. How is a shared lock different from an exclusive lock?

A shared lock allows multiple transactions to read a resource simultaneously, while an exclusive lock prevents other transactions from accessing the resource until the lock is released.

29. What is sStructural database testing?

Structural database testing is a category of database testing focused on validating the database’s internal structure, including elements like tables, columns, and relationships. This method is considered a white-box testing approach, necessitating a deep understanding of the database schema.

30. How is stored procedure testing done?

Stored procedure testing is the process of testing the functionality, performance, and security of stored procedures. It is done by executing the stored procedures with different input data and verifying the results. Stored procedure testing can be done manually or using automated tools.

The following are the steps involved in stored procedure testing:

1. Identify the stored procedures that need to be tested
2. Develop test cases for each stored procedure
3. Execute the stored procedures with different input data
4. Verify the results of the stored procedures
5. Fix any defects that are found.

31. What are the different types of database errors?

Database errors fall into four primary categories: user errors, statement errors, process errors, and media errors.

• User errors result from user actionslike inputting incorrect data or accidental table deletion.
• Statement errors arise from SQL statement issues, such as syntax or logic errors.
• Process errors occur due to database process problems, like deadlocks or transaction failures.
• Media errors stem from physical damage to the database media, such as disk corruption or file loss.

32. . What does denormalization refer to in the context of a database?

Denormalization is a strategy in database design where redundant data is intentionally stored within the database to enhance query performance. This approach diverges from the conventional practice of centralizing data in a single normalized table by distributing it across multiple locations.

33. . How many types of locks are there in a database system?

There are three main types of locks in a database system: shared locks, exclusive locks, and update locks.

1. Shared locks allow multiple transactions to read the same data but prevent any transactions from writing to it. This is the most common type of lock.
2. Exclusive locks prevent any other transactions from accessing the data, whether they want to read or write it. This is used when a transaction needs to update the data.
3. Update locks are a type of exclusive lock that allows other transactions to read the data but not write to it. This is used when a transaction needs to update the data, but other transactions still need to be able to read it.

34.. What are the various types of relationships depicted in an ER diagram?

There are three main types of relationships depicted in an ER diagram:

1. One-to-one:A one-to-one relationship between two entities means that each entity in the first entity can be related to at most one entity in the second entity, and vice versa. For example, a person can have at most one passport, and a passport can be issued to at most one person.
2. One-to-many:A one-to-many relationship between two entities means that each entity in the first entity can be related to zero or more entities in the second entity, but each entity in the second entity can be related to only one entity in the first entity. For example, a customer can place zero or more orders, but each order can be placed by only one customer.
3. Many-to-many:A many-to-many relationship between two entities means that each entity in the first entity can be related to zero or more entities in the second entity, and vice versa. For example, a product can be sold in zero or more stores, and each store can sell zero or more products.

35. How can you verify or validate the ACID properties of a database system?

There are a number of ways to verify or validate the ACID properties of a database system. Some common methods include:

1. Unit Testing: Unit testing can be used to verify that individual transactions meet the ACID properties. For example, a unit test could be written to verify that a transaction that updates a customer record will always succeed or fail as a whole and that it will never leave the database in an inconsistent state.
2. Integration Testing: Integration testing can be used to verify that transactions interact correctly with other transactions and with the database as a whole. For example, an integration test could be written to verify that two concurrent transactions that both update the same customer record do not conflict with each other.
3. System Testing: System testing can be used to verify that the entire database system meets the ACID properties. For example, a system test could be written to verify that the database can withstand a sudden power failure without losing any data.