When ER Diagrams are not enough

This is an excerpt from this article:
https://dataedo.com/blog/you-dont-need-an-er-diagram-to-understand-your-database

ERDs are good tool for documentation of data models for small, simple, well designed databases with obvious domain. But they if you try to use then to visualize real databases then they might fall short. Here are some reasons for that

Too many tables

ERDs may work if you have a couple dozen tables at most. If you put more it's going to be confusing rather than informative.

Too many columns

ERDs communicate well if they have a minimum set of columns. Some tables have over a hundred of columns and this information hides the big picture

Confusing names

Real databases have confusing, misleading names and unused tables and columns and just by looking at a name doesn't tell you anything.

What data you think this sample table in SAP holds?

Non-obvious model and domain

You probably understood data models from sample diagrams you saw easily because it describes something that is simple and you know well and understand - school classes, movie rentals, etc. Those are relatively simple processes we have contact within our lives. However, there are many domains that we don’t know, understand or are very complex with many caveats. Diagram will not explain to you what the data represents and what is its logic.

A solution?

There's no one simple solution but a good mixture of domain description, a set of simple diagrams and complete data dictionary for reference could do the trick.

See sample database documentation that works