Construct database with entity model relationship is with Entity Relationship Diagram (ERD). In model entity relationship there are three base notations, there are entity sets, relationship sets, and attributes.

This is following symbol of three base notations in entity model relationship.
Entity set -->


Relationship set -->



Attribute -->


There are some terminology is had to understand before construct database with entity model relationship, there are:

1. Super key

Super key is one or more attribute(s) which can differentiable with data row in table uniquely.

2. Candidate key

It is number of attributes which can differentiable each data row in table uniquely.

3. Relation key/Primary key

Value of relation key had to identifying a unique row in a relation. Relation key is involved of one more relation attribute. To be a primary key is an attribute had to complete candidate key objective.

4. Alternate key

Is nothing in real world, but it is created and being primary key. Alternate key is made when no one attribute in a relation which can be representing that’s relation, or any candidate key but is not effective to be primary key.

5. Composite key

Is primary key which have more than one attributes.

6. Foreign key

Is number of attributes in relation then this number of attributes is not relation key but key of another relation.

7. Cardinality

Is showing number of entity which associated with an another entity with any relationship sets. Cardinality involved:


• One to one : is one entity associated with maximum one on an entity.


• On to many: is one entity (A) associated with number of another entity(B), (B) associated with maximum one on (A) entity.


• Many to many : is number of entity(A) associated with number of entity(B) and number of entity (B) associated with number of entity(A).