Top 50 Database Interview Question

1. What is database?


2. What is DBMS?


3. What is a Database system?

The database and DBMS software together is called as Database system.

4. What are the advantages of DBMS?

I. Redundancy is controlled. II. Providing multiple user interfaces. III. Providing backup and recovery IV. Unauthorized access is restricted. V. Enforcing integrity constraints.

5. What is normalization?

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties (1).Minimizing redundancy, (2). Minimizing insertion, deletion and update anomalies.

6. What is Data Model?


7. What is E-R model?


8. What is Object Oriented model?


9. What is an Entity?


10. What is DDL (Data Definition Language)?


11. What is DML (Data Manipulation Language)?


12. What is DML Compiler?


13. What is Query evaluation engine?

It executes low-level instruction generated by compiler.

14. What is Functional Dependency?


15. What is 1 NF (Normal Form)?

The first normal form or 1NF is the first and the simplest type of normalization that can be implemented in a database. The main aims of 1NF are to: 1. Eliminate duplicative columns from the same table. 2. Create separate tables for each group of related data and identify each row with a unique column (the primary key).

16. What is Fully Functional dependency?


17. What is 2NF?


18. What is 3NF?




20. What is 4NF?


21. What is 5NF?


22. What is a query?


23. What is meant by query optimization?


24. What is an attribute?

It is a particular property, which describes the entity.

25. What is RDBMS?


26. What’s difference between DBMS and RDBMS?


27. What is SQL?


28. What is Stored Procedure?


29. What is a view?


30. What is Trigger?


31. What is Index?

An index is a physical structure containing pointers to the data.

32. What is extension and intension?

Extension -It is the number of tuples present in a table at any instance. This is time dependent. Intension -It is a constant value that gives the name, structure of table and the constraints laid on it.

33. What do you mean by atomicity and aggregation?

Atomicity-Atomicity states that database modifications must follow an “all or nothing” rule. Each transaction is said to be “atomic.” If one part of the transaction fails, the entire transaction fails. Aggregation – A feature of the entity relationship model that allows a relationship set to participate in another relationship set. This is indicated on an ER diagram by drawing a dashed box around the aggregation.

34. What is RDBMS KERNEL?


35. Name the sub-systems of a RDBMS?


36. How do you communicate with an RDBMS?

You communicate with an RDBMS using Structured Query Language (SQL)

37. Disadvantage in File Processing System?

• Data redundancy & inconsistency.

• Difficult in accessing data.

• Data isolation.

• Data integrity.

• Concurrent access is not possible.

• Security Problems.

38. What is VDL (View Definition Language)?

It specifies user views and their mappings to the conceptual schema.

39. What is SDL (Storage Definition Language)?

This language is to specify the internal schema. This language may Specify the mapping between two schemas.

40. Describe concurrency control?

Concurrency control is the process managing simultaneous operations against a database so that database integrity is no compromised. There are two approaches to concurrency control. The pessimistic approach involves locking and the optimistic approach involves versioning.

 41. Describe the difference between homogeneous and heterogeneous distributed database?

A homogenous database is one that uses the same DBMS at each node. A heterogeneous database is one that may have a different DBMS at each node.

42. What is a distributed database?


43. Explain the difference between two and three-tier architectures?


44. Briefly describe the three types of SQL commands?


45. List some of the properties of a relation?


46. Explain the differences between an intranet and an extranet?


47. What is SQL Deadlock?


48. What is a Catalog?

A catalog is a table that contains the information such as structure of each file, the type and storage format of each data item and various constraints on the data .The information stored in the catalog is called Metadata.

49. What is data ware housing & OLAP?

Data warehousing and OLAP (online analytical processing) systems are the techniques used in many companies to extract and analyze useful information from very large databases for decision making .

50. Describe the three levels of data abstraction?

Physical level: The lowest level of abstraction describes how data are stored. Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data. View level: The highest level of abstraction describes only part of entire database. 51

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