Database Concepts
- Tuesday, October 21, 2008, 7:15
- Databases
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DATABASE DEFINITION
A shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
WHY THE DATABASE IS USED?
The database is used for keeping the records electronically, which is quite safe as compared to manually. It is handy and safe, the database enables the person’s ablity to work digitally which helps the environment faster and easy. That is the common purpose of using database.
ENTITY RELATIONSHIP MODEL (ER-MODEL)
The basic concept of the Entity-Relationship Model includes entity types, relationship types and attributes. It can be defined as an object or concept that is identified by the enterprise as having an independent existence.
PRIMARY KEY
It is a Unique Value. An entity type may have more than one candidate key. For example, a member of a staff has a unique National Insurance Number (NIC) and also a unique company-defined staff number (staff No). We there have two candidate keys for the staff entity, one of the which must be selected as a Primary Key.
FOREIGN KEY
An attribute or set of attributes within one relation that matched the candidate key of some (possibly the same) relation.
COMPOSITE KEY
A candidate key that consist of two or more attributes.
NORMALIZATION
A technique for producing a set of relation with desirable properties, given the data requirements of an enterprise.
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