RDBMS Interview Questions & Answers

Q : What is a database?
A : A database is a logically coherent collection of data with the some inherent meaning, representing some aspect of real world and which is designed, built and populated with the data for a specific purpose.

Q : What is Data Independence?
A : Data independence means that "the application is independent of the storage structure and access strategy of data". In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
There are two types of independence,
Logical Data Independence: Modification in logical level should affect the view level
Physical Data Independence: Modification in physical level should not affect the logical level.

Q : What is Data Model?
A : A collection of conceptual tools for describing the data, data relationships data semantics and constraints.

Q : What is an Entity set?
A : Entity set is a collection of all entities of a particular entity type in the database.

Q : What is E-R model?
A : This data model is based on the real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

Q : Name of sub-systems of a RDBMS?
A : There are many types of sub systems in RDBMS I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery, Distribution Control, Transaction Control, Memory Management, Lock Management.

Q : How communicate with an RDBMS?
Communicate with an RDBMS using Structured Query Language (SQL)

Q :What’s the job of the information stored in data-dictionary?
A : The information in the data dictionary validates the existence of the objects, provides the access to them, and maps the actual physical storage location.

Q : What’s a database Trigger?
A : A database trigger is a PL/SQL block that can be defined to automatically execute for insert, update, and delete statements against a table. The trigger can be defined to execute once for the entire statement or once for every row that is inserted, updated, or deleted. For any one table, there are twelve events for which you can define database triggers. A database trigger can call the database procedures that are also written in PL/SQL.

Q : What is a Transaction Manager?
Transaction manager is a program module, which ensures that the database, remains in a consistent state despite of system failures and concurrent transaction execution proceeds without conflicting.

Q : What is Buffer Manager?
Buffer manager is a program module, which is responsible for fetching data from disk storage into the main memory and deciding what data to be cache in memory.

Q : What is File Manager?
File manager is a program module, which manages the allocation of space on disk storage and data structure used to the represent information stored on a disk.

Q : What is DDL?
A : A data base schema is specified by a set of definitions expressed by a special language called in DDL.

Q: What is SDL ?
Storage Definition language is to specify the internal schema. This language may specify the mapping between two schemas.

Q : What’s a DDL Interpreter?
A : DDL interprets is a DDL statements and record them in tables containing meta data.

Q : What is a query?
A : A query with respect to DBMS relates to user the commands that are used to interact with a data base. The query language can be classified into the data definition language (DDL)and data manipulation language(DML).