Here are the top 20 database testing interview questions and answers: 1) What is database testing? Database testing is a process of verifying the functionality, performance, and reliability of a database. It involves checking data integrity, consistency, and accuracy. 2) What are the different types of database testing? The different types of database testing include functional testing, performance testing, security testing, scalability testing, and data integrity testing. 3) What is data integrity testing? Data integrity testing ensures that data is accurate, consistent, and reliable. It involves verifying constraints, relationships, and rules defined in the database schema. 4) What is SQL injection? How can it be prevented? SQL injection is a technique used by attackers to insert malicious SQL statements into an application’s database query. To prevent SQL injection, use parameterized queries or prepared statements, input validation, and escape special characters. 5) What is a stored procedure? A stored procedure is a set of SQL statements that are stored in the database and can be executed repeatedly. It is used to encapsulate logic and improve performance. 6) What is normalization in database testing? Normalization is a process of organizing data in a database to eliminate redundancy and improve data integrity. It involves dividing large tables into smaller ones and defining relationships between them. 7) What is the difference between primary key and unique key? A primary key is used to uniquely identify a record in a table and cannot contain duplicate or null values. A unique key, on the other hand, allows null values but does not allow duplicate values. 8) What is the purpose of the ACID properties in database testing? The ACID properties (Atomicity, Consistency, Isolation, Durability) ensure that database transactions are reliable and maintain data integrity. They define the properties that guarantee the success or failure of a transaction. 9) What is the difference between a database and a data warehouse? A database is a collection of related data organized and structured for efficient retrieval, storage, and management. A data warehouse, on the other hand, is a large repository of data collected from various sources for analysis and reporting. 10) How do you test database performance? To test database performance, you can use techniques like load testing, stress testing, and performance monitoring. Measure response times, throughput, and resource utilization to identify bottlenecks and optimize performance. 11) What is a deadlock in database testing? A deadlock occurs when two or more processes or transactions are waiting for each other to release resources, resulting in a standstill. It can be detected and resolved using techniques like deadlock detection algorithms and resource scheduling.