One of the challenges in continuous integration for database testing is managing and versioning database schemas. As the database schema evolves with application changes, ensuring consistency and compatibility across different versions becomes crucial to maintain the integrity of the data and the functionality of the application.

Identifying and reporting bugs and defects is a key objective of database testing. This involves uncovering any discrepancies, errors, or anomalies within the database system that could affect its functionality, reliability, or security. By pinpointing issues early, teams can address them promptly, enhancing the overall quality and stability of the database application.

Data masking and obfuscation techniques are employed to safeguard sensitive data during compliance testing. By disguising or anonymizing data, organizations can ensure that sensitive information such as personally identifiable information (PII) or financial records remains protected from unauthorized access or exposure.

To improve scalability, particularly when facing issues with increasing concurrent users, horizontal scaling is a recommended approach. Horizontal scaling involves adding more machines or instances to distribute the workload, allowing the system to handle increased traffic effectively. By horizontally scaling the cloud-based database system, you can distribute the load across multiple resources, thus enhancing scalability and accommodating a larger number of concurrent users.

The primary goal of database testing is to verify data consistency and integrity. This ensures that data is accurate and reliable, which is crucial for applications relying on databases.

Manually deleting affected rows is not a recommended approach as it might lead to data inconsistency. Restarting the SQL Server service is a drastic measure and may disrupt other ongoing operations. Executing a new COMMIT TRANSACTION statement would finalize the changes, which is contrary to the goal of rolling back. The correct step is to use the ROLLBACK TRANSACTION statement to undo the changes made so far and maintain data integrity.

Access control testing involves assessing the methods used to authenticate users and enforce authorization policies. Therefore, the correct option is "Authorization," as it pertains to defining and enforcing access rights. Authentication verifies the identity of users, encryption secures data during transmission or storage, and firewalls protect networks from unauthorized access but are not directly related to access control testing.

This suggests a data integrity issue. Data integrity ensures the accuracy, reliability, and consistency of data throughout its lifecycle. In this scenario, the presence of duplicate records in the target database that were not in the source data indicates a failure in maintaining the integrity of the data during the ETL process.

Profiling in database monitoring refers to the process of monitoring and analyzing database query performance. It involves examining various aspects such as query execution time, resource usage, and query optimization to identify bottlenecks and optimize query performance. By profiling queries, database administrators can gain insights into how queries are executed and identify opportunities for improving database performance.

Test data generation tools play a crucial role in populating databases with relevant data for comprehensive testing. Relevant data closely resembles real-world scenarios and helps in uncovering potential issues that might not be apparent with random or synthetic data.