DBMS Interview Questions and Answers
DBMS Interview Questions and Answers
In this blog post, we will discuss DBMS Interview Questions and Answers (Database Management System (DBMS) Interview Questions and Answers), here we have provided you top 30 questions and answers related to DBMS which are asked in interview, that is most important for freshers and other.
DBMS Interview Questions and Answers
Question 1. What is a Database Management System (DBMS)?
Answer: A DBMS is a software application that manages, organizes, and maintains data in a database. It provides an interface between users and the database, allowing users to interact with the data.
Question 2. What are the different types of DBMS?
Answer: There are four main types of DBMS: Relational DBMS (RDBMS), Hierarchical DBMS, Network DBMS, and Object-oriented DBMS.
Question 3. What is a primary key in a database?
Answer: A primary key is a unique identifier for a record in a database table. It must be unique for each record and cannot contain null values.
Question 4. What is normalization in DBMS?
Answer: Normalization is the process of organizing data in a database to eliminate redundancy and dependency. It helps in improving database efficiency, reducing data duplication, and ensuring data integrity.
Question 5. What is a foreign key in a database?
Answer: A foreign key is a field in a database table that refers to the primary key of another table. It establishes a relationship between two tables and is used to maintain data integrity and enforce referential integrity constraints.
Question 6. What is a transaction in DBMS?
Answer: A transaction in DBMS is a sequence of one or more operations that are executed as a single unit of work. It is used to ensure the consistency and integrity of data in a database, and it follows the ACID properties (Atomicity, Consistency, Isolation, Durability).
Question 7. What is the difference between a primary key and a unique key?
Answer: Both primary key and unique key are used to uniquely identify a record in a database table. However, a primary key cannot contain null values, and each table can have only one primary key, whereas a unique key can allow null values and multiple unique keys can be defined in a table.
Question 8. What is a join in DBMS?
Answer: A join in DBMS is an operation that combines data from two or more tables in a relational database based on a related column between them. It is used to retrieve data from multiple tables and combine it into a single result set.
Question 9. What are the different types of joins in DBMS?
Answer: The different types of joins in DBMS are Inner Join, Left Join (or Left Outer Join), Right Join (or Right Outer Join), and Full Join (or Full Outer Join).
Question 10. What is the difference between a clustered and a non-clustered index in DBMS?
Answer: In DBMS, a clustered index determines the physical order of data in a table, whereas a non-clustered index is a separate structure that stores a copy of the indexed columns and a pointer to the actual data rows.
Question 11. What is a trigger in DBMS?
Answer: A trigger in DBMS is a set of instructions or code that automatically executes in response to an event or action, such as an INSERT, UPDATE, DELETE, or a specific condition, occurring in a database. It is used to enforce business rules, maintain data integrity, and automate database operations.
Question 12. What is a stored procedure in DBMS?
Answer: A stored procedure in DBMS is a group of SQL statements that are precompiled and stored in a database. It can be executed by invoking its name and passing parameters to it. Stored procedures are used to encapsulate complex logic, improve performance, and enhance security.
Question 13. What is a view in DBMS?
Answer: A view in DBMS is a virtual table that is derived from one or more base tables. It does not store any data physically but presents data from the base tables in a different format. Views are used to hide sensitive information, simplify complex queries, and provide a customized view of data to different users.
Question 14. What is a deadlock in DBMS?
Answer: A deadlock in DBMS is a situation where two or more transactions are waiting for each other to release a resource, such as a lock, resulting in a circular dependency and blocking each other’s progress. Deadlocks can lead to a system halt and require careful handling to resolve.
Question 15. What is ACID in DBMS?
Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability, which are the properties that ensure the reliability and integrity of data in a DBMS. Atomicity ensures that a transaction is either fully completed or fully rolled back, Consistency ensures that data remains in a valid state during and after a transaction, Isolation ensures that concurrent transactions do not interfere with each other, and Durability ensures that once a transaction is committed, its changes are permanent.
DBMS Interview Questions and Answers
Question 16. What is the purpose of a database index?
Answer: The purpose of a database index is to improve the performance of queries by providing a fast and efficient way to look up data. Indexes are used to speed up data retrieval operations, such as SELECT statements, by allowing the database to quickly locate the rows that match the search criteria.
Question 17. What is the difference between a unique index and a non-unique index?
Answer: A unique index in DBMS ensures that the indexed column(s) contain unique values, and it does not allow duplicate values. A non-unique index, on the other hand, allows duplicate values in the indexed column(s).
Question 18. What is a backup and recovery in DBMS?
Answer: Backup and recovery in DBMS is the process of creating copies of the database and its contents to protect against data loss due to hardware failures, software errors, or other unforeseen events. Recovery involves restoring the database to a previous state in case of data loss or corruption.
Question 19. What is data integrity in DBMS?
Answer: Data integrity in DBMS refers to the accuracy, consistency, and reliability of data stored in a database. It ensures that data is valid, conforms to predefined rules, and is free from errors, inconsistencies, and duplications.
Question 20. What is a database schema in DBMS?
Answer: A database schema in DBMS is the structure or blueprint of a database, which defines the organization of data, the relationships between tables, the data types, and constraints on data. It serves as a framework for creating, managing, and organizing the database.
Question 21. What are the different types of database constraints?
Answer: The different types of database constraints are: Primary Key constraint, Foreign Key constraint, Unique constraint, Check constraint, and Not Null constraint. These constraints are used to enforce data integrity rules and ensure that data stored in the database meets certain requirements.
Question 22. What is a database transaction log?
Answer: A database transaction log is a file that records all the changes made to a database during transactions. It captures the sequence of operations performed in a transaction, such as INSERT, UPDATE, and DELETE statements, and is used for recovery purposes in case of system failures or data corruption.
Question 23. What is a data dictionary in DBMS?
Answer: A data dictionary in DBMS is a repository that stores metadata, which is information about the structure, organization, and properties of the data stored in a database. It contains the definitions of tables, columns, data types, constraints, indexes, and other database objects.
Question 24. What is the difference between a candidate key and a superkey in DBMS?
Answer: In DBMS, a candidate key is a minimal set of attributes that uniquely identifies a record in a table, whereas a superkey is a set of attributes that uniquely identifies a record but may contain extra attributes that are not necessary for identifying the record uniquely. In other words, a candidate key is a minimal superkey.
Question 25. What are the advantages and disadvantages of using a stored procedure in DBMS?
Answer: The advantages of using a stored procedure in DBMS include improved performance due to precompilation and caching of SQL statements, encapsulation of complex business logic for reusability, and enhanced security through controlled access. However, the disadvantages of using a stored procedure include increased development and maintenance complexity, platform dependency, and potential for security risks if not properly secured.
Question 26. What is denormalization in DBMS?
Answer: Denormalization in DBMS is the process of combining two or more smaller normalized tables into a single larger table to improve query performance and reduce the complexity of join operations. Denormalization is used when the performance of data retrieval is a higher priority than the normalization of data.
Question 27. What is the purpose of the COMMIT and ROLLBACK statements in DBMS?
Answer: COMMIT and ROLLBACK are transaction control statements in DBMS. COMMIT is used to save all the changes made in a transaction to the database and make them permanent. ROLLBACK, on the other hand, is used to undo all the changes made in a transaction and restore the database to its original state in case of an error or exception. These statements ensure data integrity and consistency in a transactional environment.
Question 28. What are the different types of indexing techniques in DBMS?
Answer: There are several indexing techniques in DBMS, including primary index, secondary index, clustered index, non-clustered index, bitmap index, and B-tree index. Each indexing technique has its own advantages and disadvantages, and the selection of the appropriate index depends on the specific requirements of the database and query performance optimization.
Question 29. What is a stored procedure in DBMS?
Answer: A stored procedure in DBMS is a precompiled set of SQL statements that are stored in the database and can be executed as a single unit. Stored procedures are used to encapsulate complex business logic, improve performance, and provide a reusable and secure way to perform database operations.
Question 30. What is database replication in DBMS?
Answer: Database replication in DBMS is the process of creating and maintaining multiple copies of a database on different servers to provide redundancy, improve availability, and enhance performance. Replication can be done in different ways, such as snapshot replication, transactional replication, and merge replication, depending on the requirements of the system.
So, you learned here DBMS Interview Questions and Answers, (Database Management System Interview Questions and Answers) all these questions are very important, if you are from IT sector. I hope you have understood all questions and answers very well and if you have any doubt, regarding it then you can ask in the comment section.
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