A spike represents a sudden and significant increase in system activity or users accessing the system. It helps in evaluating how the system handles unexpected surges in workload and whether it can scale effectively.

The primary goal of database security is to secure data confidentiality, ensuring that only authorized users can access sensitive information and preventing unauthorized access.

Test automation plays a crucial role in adhering to best practices in database testing by improving efficiency and reliability. Automated testing tools allow for the execution of repetitive and complex tests with greater speed and accuracy compared to manual testing methods. By automating database tests, teams can reduce the time and effort required for testing activities, enhance test coverage, and detect defects early in the development lifecycle. Additionally, test automation facilitates continuous testing practices, enabling faster feedback loops and supporting agile and DevOps methodologies. Overall, leveraging test automation helps teams achieve higher levels of productivity, consistency, and quality in their database testing efforts.

Normalization in database testing ensures that data is stored efficiently by reducing redundancy and organizing it logically. This helps in maintaining data integrity and improves query performance. Normalization involves breaking down larger tables into smaller ones and establishing relationships between them to minimize redundancy and dependency.

Stress testing evaluates a database's performance beyond its scalability capacity to identify failure points. It involves pushing the system to its limits or beyond to determine how it behaves under extreme conditions, such as high concurrent user loads or large data volumes. Identifying failure points helps in optimizing the system for better performance and reliability.

SQL queries are commonly used by testers to compare data between source and target systems during database testing. These queries retrieve data from both systems and enable testers to perform comparisons, identify discrepancies, and validate the accuracy and completeness of data migration or transformation processes. SQL queries provide a powerful means for testers to verify the integrity and consistency of data across different systems.

Data validation in ETL processes ensures the integrity of data and verifies its completeness, guaranteeing data correctness throughout.

The unique constraint ensures that values in a column are unique within a table, thus maintaining data integrity by preventing duplicate entries.

In asymmetric encryption, the public key is used for encrypting data that can only be decrypted using the corresponding private key. Thus, the correct pair is Option 2. Option 1 is incorrect as the private key is used for decryption, not encryption. Option 3 is incorrect as asymmetric encryption is not primarily used for authentication. Option 4 is incorrect as it does not accurately represent the roles of public and private keys in asymmetric encryption.

Transparent Data Encryption (TDE) in database security encrypts data at rest, meaning the data stored on disk is encrypted. It ensures that even if someone gains access to the physical database files, they cannot read the data without the decryption key. TDE provides an added layer of security without requiring changes to the application code, making it a convenient option for securing sensitive data in databases.