To expand, SQLx isn't an ORM or query builder, what it does is allow you to write raw SQL with compile-time guarantees of type safety. It does this by connecting to a dev database at compile time & uses SQL's introspection features (specifically, by preparing a statement[1]) to analyze your queries. (It can also cache this information to check without a database available, and has a basic migration facility.)

[1] https://github.com/launchbadge/sqlx/blob/main/FAQ.md#how-do-...