multiple data base access and x platform development

I am looking for a connection tool Delphi to multiple Windows
Databases (switchable, not concurrent) and which can port to or has an
equivalent connection tool available on Linux connecting Kylix to
multiple Linux satabases.

For example, I hope to develop with Delphi under Windows with access
switchable between MySQL, Oracle and others, and be able to port to
Linux using Kylix with access switchable between MySQL and other
databases under Linux.

Can anyone suggest an optimal course of action.

Thanks