1. What is a database?
A database is a structured collection of data that is organized and managed in a way that enables easy access, retrieval, and manipulation of data.

2. What is a DBMS?
A Database Management System (DBMS) is a software that allows users to create, organize, and manage databases.

3. What is SQL?
SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases.

4. What is a table?
A table is a collection of related data organized into rows and columns in a relational database.

5. What is a primary key?
A primary key is a unique identifier for each record in a table. It is used to ensure the data integrity and uniqueness of records.

6. What is normalization?
Normalization is the process of organizing data in a database to reduce redundancy and dependency. It helps improve data integrity and efficiency.

7. What is a foreign key?
A foreign key is a field in a table that refers to the primary key of another table. It establishes a relationship between the two tables.

8. What are the different types of relationships in a database?
The different types of relationships in a database include one-to-one, one-to-many, and many-to-many relationships.

9. What is an index?
An index is a data structure that improves the speed of data retrieval operations on a database table.

10. What is a view?
A view is a virtual table derived from one or more tables. It does not store data but displays the results of a query.

11. What is ACID in the context of databases?
ACID stands for Atomicity, Consistency, Isolation, and Durability. It is a set of properties that guarantee reliable processing of database transactions.

12. What is a transaction in a database?
A transaction is a unit of work performed on a database. It is a sequence of operations that must be treated as a single entity.

13. What is a query?
A query is a request for data or information from a database. It is used to extract specific information based on specified criteria.

14. What are stored procedures?
Stored procedures are precompiled database-related routines. They are stored in the database and can be invoked whenever needed to perform a specific task.

15. What is data integrity?
Data integrity ensures that data in a database remains accurate, consistent, and reliable over its entire lifecycle.

16. What is a deadlock?
A deadlock is a situation where two or more transactions are unable to proceed because each is waiting for the other to release a lock.

17. What is the difference between a clustered and non-clustered index?
A clustered index determines the physical order of data in a table, while a non-clustered index does not affect the physical order of data.

18. What is a schema?
A schema is a collection of database objects, including tables, views, and other related entities, organized and grouped together.

19. What is data normalization?
Data normalization is the process of organizing data into tables and relationships in order to reduce duplication and ensure data consistency.

20. Can you explain the concept of data redundancy?
Data redundancy refers to the duplication of data within a database. It can lead to data inconsistency and poses a risk of data integrity issues.

1. What is a database trigger?
A database trigger is a stored procedure that automatically executes when there is an INSERT, UPDATE, or DELETE operation performed on a specific table. It allows you to enforce data consistency and integrity.

2. Explain normalization in database design.
Normalization is a process used to organize data into multiple related tables, reducing redundancy and increasing data integrity. There are several normal forms, such as 1NF, 2NF, and 3NF, which define specific criteria for data organization.

3. What is the difference between clustered and non-clustered indexes?
A clustered index determines the physical order of data in a table. Only one clustered index can be created per table. On the other hand, non-clustered indexes do not determine the physical order but provide a quicker way to look up data based on specific columns.

4. List and explain the ACID properties of a database.
ACID stands for Atomicity, Consistency, Isolation, and Durability. Atomicity ensures that a transaction is treated as a single, indivisible unit. Consistency guarantees that every transaction leaves the database system in a valid state. Isolation ensures that concurrent transactions do not interfere with each other. Durability ensures that once a transaction is committed, it is permanent and survives system failures.

5. What is a deadlock in database management systems?
A deadlock occurs when two or more transactions are waiting for each other to release resources, preventing any of them from progressing. It results in a stuck state where no progress can be made until an external intervention occurs.

6. What is a materialized view in a database?
A materialized view is a database object that stores the results of a query in a physical table. Unlike a regular view, which is a saved query, a materialized view is precomputed and stored for faster data retrieval.

7. Explain database sharding.
Database sharding is a technique used to horizontally partition a database into smaller, more manageable segments called shards. Each shard contains a subset of the data and can be stored on a separate server. It helps in distributing the workload and improving database scalability.

8. What is denormalization?
Denormalization is the process of intentionally adding redundancy to a database design to improve performance. It involves combining tables or adding duplicate data to eliminate the need for costly joins and complex queries.

9. How does indexing work in a database?
Indexing involves creating data structures (indexes) that allow for quicker data retrieval based on specific columns. It works by creating an index entry for each value in the indexed column, along with a reference to its corresponding data location.

10. What is a foreign key constraint?
A foreign key constraint is a rule that maintains referential integrity between two tables. It ensures that the values in one table’s foreign key column match the values in another table’s primary key column.

11. What is query optimization in a database?
Query optimization is the process of selecting the most efficient execution plan for a given query. It involves analyzing the query, considering available indexes, statistics, and cost-based estimations to determine the optimal way to retrieve data.

12. Explain the difference between a primary key and a unique key.
A primary key is a column or a set of columns that uniquely identifies each row in a table. It enforces data integrity and imposes a unique constraint. A unique key, on the other hand, allows duplicate values but ensures that no two rows have the same value combination.

13. What are transaction isolation levels?
Transaction isolation levels define how concurrent transactions interact with each other. They include Read Uncommitted, Read Committed, Repeatable Read, and Serializable. Each level defines the degree of isolation and the type of data visibility and concurrency control.

14. Explain database replication.
Database replication is the process of creating and maintaining multiple copies of a database across different nodes or servers. It allows for high availability, data distribution, and load balancing.

15. What are the different types of join operations in a database?
The different types of join operations include inner join, outer join (left, right, and full), self-join, cross-join (cartesian product), and natural join. Each join type serves a specific purpose in combining data from multiple tables.

16. What are triggers and stored procedures?
Triggers are automatically executed database logic in response to specific events. They are associated with tables and fire before or after events like INSERT, UPDATE, or DELETE. Stored procedures, on the other hand, are precompiled database programs that can be reused in multiple applications.

17. What is a database view?
A database view is a virtual table based on the result of a query. It presents a subset of data from one or more tables, allowing users to access and manipulate it as if it were a regular table.

18. How does the ACID property of a database ensure data integrity?
The ACID properties of a database ensure data integrity by enforcing atomicity, consistency, isolation, and durability. Atomicity guarantees that a transaction is all or nothing, preventing partial updates. Consistency ensures that only valid data is entered into the database. Isolation prevents concurrent transactions from interfering with each other. Durability ensures that committed transactions remain intact, even in the event of system failures.

19. What is a database schema?
A database schema is the structure or blueprint of a database system. It defines the tables, relationships, constraints, and other aspects of the database design.

20. Explain the difference between a database index and a database view.
A database index is a data structure used to improve the speed of data retrieval operations, primarily by allowing for quicker searching based on specific columns. A database view, on the other hand, is a virtual table that provides a customized or simplified view of data from one or more tables.