I second what Thacker Scott recomends for getting a good view of the database.
Also, if you enable "Technical Settings" for your admin user, then goto "Settings" at the bottom of the column on the left under the "Technical" section you will see a "Database Structure" menu that might be useful as well.
Actually, you can't see openerp database schema.
I recommend you to use pgAdmin III to see openerp databases and their tables and structures. pgAdmin III is used by many openerp developers. It is very helpful tool. I recommend it for you.
One can "see" the database structure (as in the database) pretty directly. Postgres can be browsed and updated w/ many client tools. Here is a good list below at the bottom of this note. Recently I have been able also to connect with FileMaker Pro which is helpful.
What I think you are really asking though is a "viewed" Index of the Database structure. I used to get this with a great Commercial package (FoxPro based) called SBT (or SBT Pro). Can't say it will be that easy to find "one compendium" for this with Odoo. Generally each Module has another pass at modifying the structure somewhat. You can look at each module to see what they are doing.
Ideally, there may be some way to "watch the data" as you work so that you could see what you are changing and when. Would seem quite practical in any event.