Learn the basics of the Entity-Relationship model for database design.
The Entity-Relationship (ER) model is a high-level, conceptual data model used to visualize the structure of a database before it is actually built. It provides a graphical representation of the logical structure, making it easy for both technical and non-technical stakeholders to understand. The ER model is built on three basic concepts. First, an Entity is a real-world object or concept that can be distinctly identified, such as a 'Student', 'Course', or 'Professor'. A collection of similar entities is called an entity set. Second, an Attribute is a property or characteristic of an entity. For example, attributes of a 'Student' entity might include 'student_id', 'name', and 'major'. Third, a Relationship is an association between two or more entities. For example, an 'Enrolls' relationship associates a 'Student' with a 'Course'. Relationships have a cardinality that specifies the number of instances of one entity that can be related to instances of another entity (e.g., one-to-one, one-to-many, many-to-many). ER diagrams are the visual tool used to represent this model, using rectangles for entity sets, ellipses for attributes, and diamonds for relationship sets. This modeling technique is a crucial first step in database design, as it helps designers clarify requirements and create a blueprint that can then be translated into a relational database schema.