C++ database access

I'm designing a new large project which uses database intensively.
I'm looking for a c++ library that provides access to databases (such as ilog and dtl) that has the following features:
* unicode support.
* good benchmarks.
* support multithreading.
* high reliability.
* multi-platform.
* supports several db engines (e.g. oracle, sybase, ms sql...).

Does anyone familiar with such library?

TIA,
Yaniv.

There is no multiplatform database standard. For Windows you should look at OleDb. Its the only technology that does everything you mention.