Does Oracle have a tool I can use to analyze a database and help determine possible missing field relationships? We have a legacy database with 150+ tables and many relationships are missing. We could go through it by hand but an automated tool might be useful. So find things like missing foreign keys and whatnot.
I've had to do this a few times now. I find it's a very human-intelligence kind of thing - helped by running a lot of queries across both the data dictionary (e.g. EvilTeach's query), querying sample data from the columns, examining how the data is created by the application, and understanding the business requirements and user processes.
For example, in many legacy applications I find constraints (including referential integrity constraints) that are checked and implemented in the front-end application, which means the data follows the constraint (almost 100% :) ) but it's not actually constrained at the database level. Lots of fun results.
I'd be surprised if a tool could do any of this automatically and yield useful results.