了解如何在不使用SQL的情况下理解组织结构

I am joining a new company in which there are no Entity relationship diagrams. However the Primary and Foreign key constraints exists. The database is in SQL server, I just want what the best and fastest way to develop an understanding using the SP or querying in SQL would look like to best understand the relationship between tables and to map how everything is laid out.I am joining a new company in which there are n