This used to be how a lot of SQL code was written. I think it's about as old as SQL itself. See Oracle's Pro*C for instance. It's a C precompiler that generates API calls and optionally does type checking. There's even an ANSI/ISO standard for embedded SQL.
Yep. I used to use the Sybase SQL precompiler in OS/2 with Watcom C++. Nullable columns were a pain because you had to define a separate boolean variable to hold the null status for each one.
