Pinderkent

Anybody working on business applications these days will undoubtedly have to familiarize himself or herself with one or more existing databases. These databases have often been "grown" rather than designed in any meaningful way, and thus will be littered with unused tables, unused functions or stored procedures, missing constraints, poor normalization, and a host of other problems.

Developers in such a situation will often look for an easy way out, such as the use of tools to automatically reverse-engineer various parts of the existing database or databases. While these tools can be useful, I don't think they are ever a replacement for just stepping through the code, line-by-line, and observing exactly what queries are executed.

Depending on the application, it may even be a bad idea to try and think of the application and database as separate. Many times we find that one can't exist without the other, and vice versa. For instance, we find hard-coded SQL queries within the application code written in languages like Java, PHP or C#. In such situations, one literally has to take a debugger and step through the application code in order to get even a basic understanding of how the system works.

Another thing that may be worth avoiding is trying to understand the system all at once. Often, it will take many months to truly grasp even a moderately sized application and the database behind it. As changes are made or bugs are fixed, take a moment or two to study and document the code paths that are involved. Doing this on a daily basis will eventually expose a developer to large portions of the software system they're working with.

Regardless of the approach, one thing to keep in mind that it's not an easy task becoming familiar with existing codebases and databases, especially when they're as ugly as so many real-world systems are. Give it time, remain patient, and eventually the system will start to feel much smaller and manageable.