The YB.ORM library aims to simplify writing C++ code that has to deal with SQL databases. The goal is to provide a convenient interface like SQLAlchemy (Python) or Hibernate (Java). The library itself is cross-platform and supports a variety of SQL dialects: SQLite3, MySQL, Postgres, Oracle, and Firebird. Integration with Boost, Qt4, and wxWidgets is built-in. In a typical usage scenario, you would describe your database schema and table relationships in a simple XML-based format, generate SQL code to populate database schema with tables, generate C++ classes, add application-specific logic to the classes, and use these classes in cooperation with the Session object to query objects from the database, create new or modify/delete existing objects, or link and unlink objects using relations. Simple serialization to XML is supported along with connection pooling.
NNDB is a C++ library that provides in-memory data storage and retrieval using syntax that is intended to feel natural for C++/STL, but which also might feel slightly like SQL if you squint and pound the top of your head with a seminal programming textbook. Columns types are fixed at compile-time and checked by the compiler.