Relational database management systems (RDBMSs) often persist mission-critical data which is updated by many applications and potentially thousands if not millions of end users.  Furthermore, they implement important functionality in the form of database methods (stored procedures, stored functions, and/or triggers) and database objects (e.g. Java or C# instances).  The best way to ensure the continuing quality of these assets, at least from a technical point of view, you should have a full regression test suite which you can run on a regular basis.