In practice, it's actually pretty rare for a GraphQL schema (exposed to clients) to be identical to a database schema which often has admin-only columns or database-specific idiosyncrasies like SQL join tables that you would opt to expose differently to a client.

That being said, there's a lot of low hanging fruit for building a GraphQL schema "generator" libraries for various backing databases - while some things are likely to change, it's quite nice to just apply those edits rather than building up a near-parallel schema again.