Entity Relationship Modelling

I started filling out Excel worksheets with column names for a DB I'm creating for my DMT class. Each worksheet represented a table in my DB. I realised that my brain would soon explode unless I had some way of plotting how the tables related to eachother. I searched the web and found two gems...

The first is a library of exisiting database schemas for common systems <http://www.databaseanswers.org/data_models>. These are handy blueprints to have and I recommend that my fellow DMTers browse through it (unfortunately, it didn't have anything that quite fit what I'm building). What I got out of it was being reminded of the notation that's used in Entity Relationship models (I was also reminded of the term "Entity Relationships"!).

originally proposed by Peter in 1976 [Chen76] as a way to unify the network and relational database views. Simply stated the ER model is a conceptual data model that views the real world as entities and relationships.

(http://www.utexas.edu/its/windows/database/datamodeling/dm/erintro.html viewed 14th May, 2007)

The part I love most about ER modelling is the notation used. Once you learn it, it makes you feel smart - and it's so easy. Any time-poor sod can learn it within a few minutes. "Crows feet" and "one-to-many" relationships etc. the following diagram sums it up really well. Can't wait to add it to my System Plan, I almost feel like a real IT geek.

Click here for full-size image.