I'm a strong advocate of putting as much logic as possible directly into the database. That means incorporating it in views and stored procedures. I believe that most follows the DRY principle.
For example, consider a table with FirstName and LastName columns, and an application that frequently makes use of a FullName field. You have three choices:
Query first and last name and compute the full name in application code.
Query first, last, and (first || last) in your application's SQL whenever you query the table.
Define a view CustomerExt that includes the first and last columns, and a computed full name column and then query against that view, rather than the customer table.
I believe option 3 is clearly correct. Consider the addition of a MiddleInitial field to the table and the full name computation. Using option 3, you simply need to replace the view and every application across your company will instantly use the new format for FullName. The view still makes the base columns available for those instances in which you need to do some special formatting, but for the standard instance everything works "automatically".
That's a simple case, but the principle is the same for more complex situations. Perform application- or company-wide data logic directly in the database and you do not need to concern yourself with keeping different applications up to date.
