Interview Terminology of Databases

Terminology of Database

Table of Content

• ·         What is the difference between fixed-length and variable-length fields?
• ·         What is table or relation?
• ·         Define Entity?
• ·         Define tuple?
• ·         What is an attribute?
• ·         How a relation is formed?
• ·         Write different properties of a relation.
• ·         What is view?
• ·         What is the purpose of using views?
• ·         What is Key?
• ·         Who is user or end-user?
• ·         Who is a data administrator?
• ·         Who is database administrator?

What is the difference between fixed-length and variable-length fields?

A Field that has fixed size and its size cannot be change when data assigned to it is called fixed-length field. A field whose size may be changed by file management system at the time of data entry into it is called variable-length field.

What is table or relation?

A set of named columns and set of rows is called relation. A relation is also called as table. The fields are written as columns of the table. The data of different records is written under the columns of the table

Define Entity?

Anything in the real world that has a set of different attributes or properties is known as entity

Define tuple?

Each row in a relation represents a single record. Each row is also known s tuple or occurrence in that relation.

What is an attribute?

The name columns of the relation are called attribute in a relation each attribute has a unique name.

How a relation is formed?

The data about an entity is collected and stored in table or relation of database. A relation is formed by converting the attributes of entity into columns. The name of the entity is given as relation name.

Write different properties of a relation.

The properties of a relation are as follow:

No Duplicate row exist

The order of rows is insignificant

The order of columns in insignificant

Columns / attribute are all elemental or atomic

What is view?

Presentation of data for users is known as data view. By using this feature of BDMS, same data of database can be viewed in different ways and formats. The data from several relations of database can retrieved and presented to the user as one relation.

What is the purpose of using views?

The purpose of using views is to hide the confidential data of database from un-authorized and illegal user. Only the particular data of database is presented to the users according to their specific needs. Therefore, views provide a level of data security.

What is Key?

A key is an attribute or set of attributes of a relation. Key are defined in the relations for the following purposes:

For uniquely identifying the records of relation

For establishing relationships between relations.

For quickly accessing particular records from the relation / table.

For scoring records of a relation based on the data of one or more columns.

Who is user or end-user?

The users or end-users are the people who use the DBMS to perform Different operation on database. The end users need not have complete knowledge of computer system and databases. They can install new software and operating systems into the computer.

Who is a data administrator?

Data administrator is a person who is responsible for the entire data resource of an organization. He develops functional requirements for the database being used in te organization. The main job of data administrator is to decide what data should be stored in the database. He/ She also established policies for maintain data, once it has been stored. Usually, Data Administrator is a manager of the organization and not an it professional.

Who is database administrator?

The database administrator (DBA) plays very important role in DBMS environment. The DBA is responsible for designing, coordinating and monitoring the database system. The DBA is an it professional. He must be technically competent having excellent communication and management skills