Database design for database-agnostic applications

Question

What do I have to consider in database design for a new application which should be able to support the most common relational database systems (SQL Server, MyS

Answer 1

95% portable is nearly as good as portable if you can isolate the platform-dependent code into a specific layer. Just as Java has been described as 'Write once test everywhere', one still has to test the application on every platform you intend to run it on.

If you are circumspect with your platform specific code you can use portable code for the 95+% of the functionality that can be done adequately in a portable way. The remaining parts that need to be done in a stored procedure or other platform-dependent construct can be built into a series of platform-dependent modules to a standard interface. Depending on the platform you use the module appropriate to that platform.

This is the difference between 'Test everywhere' and 'Build platform specific modules and Test everywhere'. You will need to test on all supported platforms anyway - you cannot get away from that. The extra build is relatively minor, and probably less than making a really convoluted architecture to try and do these things completely portably.