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.

Indexing improves database query performance by speeding up data retrieval. It works by creating an optimized data structure that allows the database management system to locate rows more efficiently based on the indexed columns. This helps reduce the time required to execute queries, especially for large datasets, resulting in faster response times for users.

Implementing covering indexes ensures that all required columns for a query are included in the index itself, eliminating the need to access the actual table data for retrieval. This approach enhances query performance without affecting data insertion speed.

Authorization testing verifies that only authorized users have access to the database. It involves validating user credentials, permissions, and roles to prevent unauthorized access.

Database testing ensures the integrity of data, ensuring that it maintains its accuracy, reliability, and consistency throughout various operations such as insertion, deletion, and retrieval.

Query tuning involves analyzing and modifying SQL queries to make them more efficient in terms of execution time and resource usage. This process often involves examining query execution plans, indexing strategies, and data retrieval methods to optimize performance.

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.