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This Entity-Relationship diagram example (ERD) visually describes the typical process of a customer paying their cell phone bill. Not to jump to conclusions, but if you clicked on this post, you probably know that the Entity-Relationship Model is used for describing data and the relationship between different entities in a database. And just in case you're rusty, here's a refresher on what they're all about.
ERDs create a visual map, outlining process requirements and showing connections between entities and their attributes. Originally the brain child of Peter Chen, the ERD was created in the mid-1970s, but over time, it has been modified and updated. If you’d like more detailed info along with a description of the symbols and their meanings, check out this article.
To delve in just a bit further, remember that most ERDs live on one of three levels: the conceptual, the logical or the physical.
The Conceptual Level: think of this as a bird’s eye view. At this level you’ll look at entities and their relationships without using attributes and keys.
The Logical Level: this is a more zoomed in view where you’re looking at how the data will be utilized in a database. Here, you’ll use entities, attributes and keys.
The Physical Level: this is the most zoomed in of the three levels. It looks at the physical processes involved (like the above free template). It uses all the symbols and looks at table structure, column information, primary and foreign keys and relationships among tables.
Entity-Relationship diagramming is crucial to thinking about how to set up your database structure and are one of the basic building blocks when taking on a database structure project. Creating an ERD before delving deeper can save a lot of time, missteps and frustration later down the line.