Example of ERD – The term ERD is often heard in the development of information systems. In simple terms, ERD is a form of database modeling. This is an Entity Relationship Diagram, this is a model to explain the relationship between data in the database based on the basic data objects that have relationships between relationships.
Ok, if you don’t understand and don’t know what ERD is, what is the meaning, method, ERD notation to for example, don’t worry because we will clearly review ERD in for all of you. We start right away with the understanding of ERD itself.
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Understanding of ERD
In software engineering, ERM or Entity Relationship Model is a form of abstract representation of data. Meanwhile, entity relation is a database model method that is designed to produce a contextual schema for the semantic data type of the system.
The diagrams used to draw the form of entity relations are called ER diagrams or ERDs. So, what is the real understanding of ERD, let’s look at the reviews of the following experts:
1. Sutanta (2011: 91)
Sutanta mentioned in a title “Database in Conceptual Review” that “Entity Relationship Diagram (ERD) is a data model whose development is based on objects”.
2. Mata-Toledo and Cushman (2007: 139)
They both said that “Entity Relationship Diagram (ERD) is a graphical representation of the database by including a detailed description of all entities (entities), relationships (relationships), and constraints (constraints).”
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3. Brady and Loonam (2010)
Brady and Loonam mentioned that ERD is a technique designed in such a way by modeling the data needs of an organization. This is usually done by systems analysts in analyzing the stages of a development project.
Those are some of the definitions of ERD or Entity Relationship Diagram, so we can conclude that ERD is a graphical description of a data model by including a detailed description of all entities, relations, and constrains, which aims to meet the analyst’s system when completing the development of a system. .
ERD function (Entity Relationship Diagram)
Ok, after we understand and know the definition of ERD based on the experts, now we also need to know what exactly is the function of a graphical representation of this data model. Here are some functions as quoted from ngertiaja.com:
- Make it easy to analyze a data system quickly and cheaply.
- You can make a test on the model you created and you can also ignore the process that has been made quite easily by simply describing the ERD.
- Describe the relationship between data in the database in accordance with the basic objects of a data.
- Documenting existing data by signifying and identifying each entity from that data and its relationship to an Entity Relationship Diagram (ERD).
ERD notation
ERD in modeling data structures and relationships between data uses several symbols and notations. Regarding ERD notation there are several conventions:
In the Entity Relationship Diagram, notations and symbols are used. The notations and symbols used in this case are entities, attributes, relationships and lines.
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1. Entities
This is everything that can be described by data, it can also be interpreted as something real and existing but can be distinguished from something else (Fathansiah, 1999). The basic object can be anything, people or other objects and information about the necessary and important objects is stored in the database.
Entities are classified into two types, namely strong and weak entities. A strong entity is an entity that can function independently without the need for other entities, while a weak entity is an entity that in its emergence depends on other entities.
2. Attributes
The Attributes are descriptions of the type of an entity by providing detailed information about that entity. Attributes consist of an internal structure in the form of data, the types of attributes can be divided into several types, such as:
- – Key attribute
- – Simple attribute
- – Multivalue attribute
- – composite attributes, and
- – Derivative attributes
3. Relationships or relationships
A relation or relationship is a form of ERD notation that forms a relationship between entities that come from several different entities.
4. Lines
The line is a means of connecting the set of relations, entities and attributes.
