Entity-relationship model: What is it and what is it used for?Tecnología | Artículo
- Agosto 2022
The Entity-Relationship Model is something you definitely need to know about if you work with a database. Databases are widely used in business. They are essentially the virtual equivalent of a storage unit. They can store all the information about employees, customers, etc. If the data within a database is disorganized, it is nearly impossible to navigate.
Database Management Systems make it easy to create, update, and organize databases. The Entity-Relationship Model is a tried and true database management system that allows users to visually see the components of their database and the ways in which they are related to each other.
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What is the Entity-Relationship Model?
Also known as the Entity-Relationship Diagram, it serves as a simple and easy way to view a database. At times, databases can be designed in complex ways that can make them a bit difficult to navigate. This model gives database end-users, programmers, managers, and designers the ability to better understand a database and more efficiently communicate with one another. Everything to know about a certain database can be depicted in the Entity-Relationship Model, which has been used since its introduction in 1976.
What are the Components of the Entity-Relationship Model?
The diagram is made up of two different parts: entities and relationships. A database is formed by a variety of entities, all of which have relationships with one another.
What are the Entities?
An entity is a person, event, object, place, or concept from the real world for which data is being collected and stored within a database. Within the model, they are represented by a rectangle. The name of each entity is written inside each rectangle. These entities have their own specific qualities, or attributes, which allow them to be distinguishable from other entities. Entity sets are formed when certain entities have similar qualities. For example, in a business’ customer database, each customer would be considered their own entity. Each specific customer’s contact information, locations, and purchases would all be considered the attributes of the entity. All the customers within the database that live in Florida could be considered an entity set. There can also be what is called a weak entity, which is when an entity is not easily identifiable by its qualities alone and needs to have been characterized based on its relationship to another entity within the database. For example, if a business has an email address in its database without the name of the customer it belongs to, it would be considered a weak entity. In the Entity-Relationship Model, a weak entity is illustrated by a double rectangle.
Attributes of the Entity-relationship model
All attributes have some sort of value, which depends on the type of attribute it is. All attributes have a domain, which is a set of potential values an attribute could have. It could be a wide range of many different values, or it could be something more specific. For example, the domain for customers’ locations could be extremely broad. Depending on where a company’s services are offered, the domain could consist of countries all over the world. On a smaller scale, the domain for customers’ shoe size could range from a size 6 to a size 12. There are many different kinds of attributes: simple, composite, derived, single-value, and multi-value. A simple attribute is one that cannot be further divided, ie. a customer’s email address. A composite attribute is one that can be further divided, ie. a customer’s location which can be divided into city and state. A derived attribute can be derived from other attributes within the database, ie. the total number of purchases a customer has made. A single value attribute only has one single value, ie. a customer can’t have more than one birthdate. A multi value attribute has more than one value, ie. a customer can have multiple shipping addresses.
A relationship connects entities to one another. It is shown as a diamond in the Entity-Relationship Model. Entities and relationships are connected by lines. There are a few different kinds of relationships: one-to-one, many-to-one, one-to-many, and many-to-many. In a one-to-one relationship, one entity is related to another, ie. a customer has a specific home address, which belongs to that specific customer alone. In a many-to-one relationship, there are multiple entities that are related to one entity, ie. many customers live in the same state. In a one-to-many relationship, one entity is related to multiple entities, ie. a customer ordered multiple different products. Finally, in a many-to-many relationship, many entities are related to many entities, ie. many customers used many different discount codes.
The Entity-Relationship Model is a simple and extremely useful database management tool that allows for a database to be navigated based on its entities, their many attributes, and their relationships to one another. It provides all the necessary information in a visual representation that has been used for decades.
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