This is just a simple ER diagram, in this example, we were planning on partially integrating with an enterprise standard database which was not able to be modified, an external database with additional custom fields, and two systems maintained by other companies. I started my career as a programmer, not a very good programmer, but a programmer nonetheless. The one thing I was good at technically was understanding databases at a deep level. I get structure, I like planning it, I can get intimately involved with the data, and often do full content inventories and migration plans when I work on system upgrades and replacements.