I've released an open-source library called quince (QUeries In C++ Expressions) that helps you access PostgreSQL from C++. I know, I know: you've got plenty of those already, but this one is different ...
It's an EDSL (Embedded Domain-Specific Language), which lets you build sophisticated SQL queries in C++ syntax with C++ data types, and it's also an ORM, which figures out how to represent your C++ structs/classes/tuples as multiple columns. It's a plain old library, so no special compiler and no code generation step. And fwiw it works with sqlite too (and maybe other DBMSes in the future -- it's a matter of adding backend libraries).