There’s this whole thread about string handling. Does the Rust API into SQLite not support prepared statements?
Mucking about with SQL strings, to me, is akin to writing your own crypto: Don't. Unless you must (because, say, it doesn't exist yet.) Doing this is asking for security problems later. Trust that the SQLite team (or any other SQL engine) have more experience and have provided a correct interface. And if that interface isn't correct, don't just run off an make your own- contribute a fix so we can keep all the lessons learned together.