Authorization ensures that only authorized users can access specific data within a database. Authentication verifies the identity of users before granting access rights.

When a previously passing test script fails unexpectedly, verifying recent changes in the application code or database schema is crucial. Any modifications or updates could have introduced errors or inconsistencies, leading to the failure. By reviewing the changes, developers and testers can pinpoint potential causes and take corrective actions promptly. This ensures the stability and reliability of the test scripts and the overall application.

Intermittent test failures in database scripts could result from data dependencies or conflicts arising from concurrent test executions. When multiple tests manipulate the same data simultaneously, it can lead to inconsistent outcomes, causing intermittent failures. To troubleshoot this issue, identifying and resolving data dependencies, ensuring proper synchronization between test steps and transactions, and implementing mechanisms to manage concurrent access to shared data are essential steps. This ensures test scripts execute reliably and produce consistent results.

Handling large data sets in a database often poses the challenge of scalability, where traditional database systems struggle to efficiently manage and process vast amounts of data. Scalability refers to the ability of a system to handle increasing amounts of workload or data without compromising performance or responsiveness.

Checksums are a method used to detect errors in data transmission or storage by calculating a unique value based on the content of the data. Comparing checksums before and after transmission or storage helps identify any changes or corruption that may have occurred.

Data consistency and accuracy are crucial aspects of database testing. Implementing data validation checks ensures that the data entered into the database meets certain criteria, thus maintaining consistency and accuracy. This involves validating data types, constraints, and relationships to ensure they adhere to predefined standards. Performing data reconciliation helps identify discrepancies between different datasets or systems, aiding in maintaining data accuracy.

A SELF JOIN is a regular join but with a table being joined to itself. In this scenario, you can use a SELF JOIN on the employee table, matching the ManagerID in the table to the ID of another employee to retrieve the names of all employees and their respective managers.

In a subquery, the EXISTS operator can be used to compare a single value with a result set. The EXISTS operator returns true if the subquery returns any rows, otherwise false. It is commonly used in correlated subqueries to check for the existence of a particular condition. For example, you can use EXISTS to check if there are any employees in a department with a certain job title.

In a database table, the column often used as the basis for creating an index is the primary key. A primary key uniquely identifies each record in the table, making it an ideal candidate for indexing to improve data retrieval speed. Indexing the primary key allows for fast lookup and retrieval of specific records based on their unique identifiers. Other columns, such as foreign keys, unique constraints, or timestamps, may also be indexed based on the specific requirements of the application and the types of queries being executed. However, primary keys are the most common choice for indexing in database tables.

Monitoring and profiling tools assist in database capacity planning by tracking resource usage and predicting future requirements. These tools monitor various aspects such as CPU utilization, memory usage, disk I/O, and network traffic to understand the current workload on the database server. By analyzing historical data and trends, database administrators can forecast future resource requirements and plan for capacity upgrades or optimizations to ensure optimal performance and scalability of the database system.