How to handle db constraint violations in the user interface?

Question

We implement the majority of our business rules in the database, using stored procs.

I can never decide how best to pass data constraint violation errors from the databa

Answer 1

The problem is really one of a limitation in the architecture of your system. By pushing all logic into the database, you need to handle it in two places (as opposed to building a layer of business logic that links the UI with the database. Then again, the minute you have a layer of business logic you lose all the benefits of having logic in stored procs. Not advocating one or the other. The both suck about equally. Or don't suck. Depending on how you look at it.

Where was I? Right.

I think a combination of 2 and 3 is probably the way to go.

By pre-empting the error you can create a set of procedures that can be called from the UI-facing code to provide detailed implementation-specific feedback to the user. You don't necessarily need to do this with ajax on a field-by-field basis, but you could.

The unique constraints and other rules that are in the database then become the final sanity-check for all data, and can assume that data is good before being sent, and throw Exceptions as a matter of course (the premise being that these procedures should always be called with valid data and therefor invalid data is an Exceptional circumstance).