and Email of a students
are his attributes. Attribute name
*A set of possible values for an
*All atributes have domain
Example : The domain for Grade
point average (GPA) can be from 0
*A logical connection between different enities.
* Established on the basis of interaction between these
Participents: entities participating In a relationship are
Doctor treats Patient
Teacher teaches students
If all entities of that entity set may be participant in
Example: In supplier_part relationship,the
relationship is total if every part is supplied by a
If some of the entities of that entity set may be
participant in the relationship.
Example: If certain parts are available without a
*Cannot be subdivided into smaller
*Can be divided into smaller components.
Contain single valued value.
Contain two or more values.
*Stored in a database.
*Not stored in database but derived
from another value.
Identifies an entity
instance among other
instances In entity class.
week entity Can exist only if any other entity
exist, also called child ,dependent .
Strong entity Can exist without depending upon the
existance of another entity .
PERSON HAS CHILDCHILD
entity on which the
weak entity depends.Example
Type of entity that associates the
instances of one or many entity type
with one another.
•The number of entities in a relationship .
•1: unary relationship
•2: binary relationship
•3: ternary relationship
Exist between the instances of two