It is used in File Management System.

It is easy to maintain and modify the existing code.

It is used by people who don't know how database is implemented.

It does not describe cardinality

It consists of components like domain, attributes, tuples.

Some of the popular Language and Notations used:
• Chen
• UML • Crow's foot • Bachman and others.

Defines both schemas.

Allows retrieval, insertion, deletion, modification

Database management systems can be classified based on several criteria,such as the data model, user numbers and database distribution.

Centralized, Distributed

It can be a single-user database system, which supports one user at a time, or a multiuser
database system,

was introduced by C. F. Codd in 1970. Currently, it is the most widely used data model

The order of attributes has significance

Each attribute has … name;

Each tuple is distinct; there are no duplicate tuples;

The order of tuples has significance, theoretically

Each cell of the relation contains exactly one atomic (single) value;

The values of an attribute are all from the same domain;

The candidate key that is selected to identify tuples uniquely within the relation.

Candidate key: when a key consists of more than one attribute

Super key : An attribute, or set of attributes, that uniquely identifies a tuple within
a relation.