Asking SQL schema by FOIA
Let's suppose the institution does send me a listing of all the tables and their columns.  Even though I don't have the actual data, I can now attempt social engineering attacks to convince insiders into giving me whatever data I want. 

The request would sound much more legitimate, because I could ask for very specific pieces of information using the actual table names. If I were to find someone with access to the database and convince them that I'm a higher-ranking employee (e.g. their manager or the CEO), I could make a legit-sounding request for sensitive information. 

You would be surprised how often this happens in a corporate environment. Just having the metadata for a database exposed can be a big security risk.