ENTITY-RELATIONSHIP DIAGRAMS & NORMALIZATION

ENTITY-RELATIONSHIP DIAGRAMS 

Entity-Relationship Diagram (ERD) is a model that shows the logical relationships and interaction among system entities. Unlike data flow diagrams, entityrelationship diagrams depict relationships, not datanor information flows.

Three types of relationships can exist between entities: one-to-one, one-to-many, and many-to-many.

 

Gambar 1: Contoh ERD one to one.

Gambar 13: Contoh ERD one to many.

Gambar 2: Contoh ERD many to many.

Cardinality

We must define the relationships in more detail by using a technique called cardinality. Cardinality describes the numeric relationship between two entities and shows how instances of one entity relate to instances of another entity. A common method of cardinality notation is called crow’s foot notation because of the shapes, which include circles, bars, and symbols, that indicate various possibilities.

Gambar 3: Crow’s foot notation.

Gambar 4: Contoh notasi Cardinality.

NORMALIZATION

Normalization is the process of creating table designs by assigning specific fields or attributes to each table in the database. The normalization process typically involves four stages: unnormalized design, first normal form, second normal form, and third normal form.

Normalization is a process for avoiding problems in data design.

Penulis: Yusia /Kaleb

Referensi:
[1] Shelly, G.B., Rosenblatt, H.J., Systems Analysis and Design Ninth Edition. Course Technology. 2012. Boston, USA.