Business analysis glossary
Entity Relationship Diagram (ERD)
What it is
An entity relationship diagram is a picture of a data model. Boxes represent entities such as Customer or Order, and lines show relationships such as one-to-many, often with the key fields listed. Typical notation includes crow's foot symbols that show whether a relationship is one-to-one, one-to-many or many-to-many.
Why it matters
It gives analysts, developers and data people one shared map of the data, so questions like "where is the delivery address stored?" are quickly answered. Analysts use it to write precise data requirements and to discuss reports with developers without ambiguity.
Example
The ERD for Cedar Credit Union shows Customer linked to many Accounts, and Account linked to many Transactions. Reading it, the analyst sees transactions have no direct link to the customer and must be joined through accounts. Such discoveries help the analyst write the right query or ask the right question before a report is built on a wrong assumption.