Re: transparent/backend migration

[Anders Karlsson]

Possible, yes, but not an easy task. In addition, creating a complete and transparent solution is hardly worth the effort. What I would recommend instead is a tool to aid in migration with minimal application changes, and supporting tools for identifying where changes needs to be done, and what those changes are. Some issues to look for here are:
- SQL Syntax. Most SQL databases have SQL standard extensions, and often the limitation and semanitics differ, as this is not always documented in the standard.
- The API. ODBC / JDBC helps, but will not be complete, as there are different levels of support within these API's.
- Optimizations. Some SQL constructs which are very effective in database A, might be a disaster with database B.

Using an OR mapping tool will make this process much more transparent, but on the other hand limits what you can do with the SQL syntax, and creates an overhead in and of itself. And of course this is only applicable if the application is built to use such an OR tool.

Best regards
Anders Karlsson
BTW. Building a tool that understands Oracle SQL and converts that, in runtime, to MySQL SQL would be an interesting task, at least to begin with. But it would take some time....