Decipher database schema [closed]

Answer 1

What DBMS (Database Management System) are you using? Many modern DBMS's like SQL server and Access can create an E-R diagram for you.

Microsoft Visio is an excellent tool and can reverse engineer SQL from any datasource.

DDT (Database Design Tool) can reverse engineer from raw SQL on windows and is very lightweight (very small free download).

MySQL Workbench is one of the more popular MySQL tools and has a freely downloadable version.

SQLFairy can do the same for MySQL on Linux.

Answer 2

Try DBVis - download at http://www.minq.se/products/dbvis/ - there is a pro version (not needed) and a open version that should suffice.

All you have to do is to get the right JDBC - database driver, the tool shows tables and references orthogonal, hirarchical, in a circle ;-) etc. just by pressing one single button. Enjoy!

Answer 3

Look at the primary key foreign key relationshsips that have been set up as a starting place.

Since a database without existing diagrams, may not have relationships set up formally, I look at the table structures and names and make my best guesses as to what might be related to what, then dig into the structures to see if there are obvious (but undefined) foreign keys. I look at the stored procs to get an idea as to how the tables are joined and what fields are being queried on.

While automated tools to figure out the database can be spiffy, I find that when I really dig into the details of the database myself, I end up with a much better understanding than I can get from any picture created automatically.

Answer 4

Firstly, may I say that I feel your pain!
Here are a couple of my tips:

1. In general, a tool will only be helpful if the designers have correctly defined all the primary and foreign keys, so be aware that a tool might not pick up all the important relationships.
2. The most useful thing is to see what queries are being performed by the client code. This will tell you not only what relationships exist, but which tables and relationships are the most frequently used - that's where you'll want to concentrate your effort.

Answer 5

I like to try and see if the applications that use the database have ways of logging the SQL they use (or the DB backend itself, but that tends to be less tractable). Getting a feel for what requests performed on the database helps you concentrate on the important tables.

As with most things, the 80/20 rule applies here: 20% of the tables will do 80% of the interesting stuff. Once you've figured them out, a diagram is rarely necessary.

Answer 6

I have some pretty good experience with Aqua Data Studio for reverse engineering a DB schema. It is very feature rich and supports even more exotic databases like Informix or Sybase.