Entity relationship diagram
An Entity Relationship Diagram (ERD) is a visual way to describe how data is organized in a system. It shows the main “entities” (things you store data about, such as Customers or Orders), the “relationships” between them (how entities connect, such as a Customer places Orders), and the “attributes” of each entity (fie
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Entity Relationship Diagram (ERD)
An Entity Relationship Diagram (ERD) is a visual way to describe how data is organized in a system. It shows the main “entities” (things you store data about, such as Customers or Orders), the “relationships” between them (how entities connect, such as a Customer places Orders), and the “attributes” of each entity (fields like CustomerID, Name, or OrderDate). ERDs are commonly used in database design to clarify requirements before building tables and constraints.
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Common components
ERDs typically include: (1) Entities, represented as boxes; (2) Attributes, listed within or connected to entities; (3) Relationships, shown as lines between entities; and (4) Cardinality/optionality, indicating how many instances are involved (e.g., one-to-many, one-to-one, many-to-many) and whether participation is required or optional. Some ERD styles also show keys (primary/foreign) and constraints that help enforce data integrity.
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Why ERDs are useful
ERDs help teams align on data meaning, reduce ambiguity, and support consistent implementation in relational databases. They can be used for documentation, communication with stakeholders, and as a blueprint for translating the design into tables, columns, and relationships.
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