Great article, I really like your approach. Working in ETL, I too often have to look at unfamiliar data, with guidance that is missing or unreliable, and it's great having a toolkit to examine such data. I wrote some code that will examine a table and determine possible natural keys for it: http://www.sqlservercentral.com/scripts/T-SQL/62086/. You might want to consider adding it to your toolbelt. 🙂