Schema migrations with sqlx-cli

SQLx comes with its own migration tool, sqlx-cli. sqlx migrate add create_orders creates a timestamped SQL file in migrations/, and the -r flag gives each migration a matching down file to undo it. sqlx migrate run applies the pending ones and records them in a table, so every environment reaches the same schema.

You can also embed the files in your binary with sqlx::migrate!() and run them from code. The query macros read the live schema, so apply migrations before you build. Run them as a separate deploy step rather than at every app start, so several copies of the app do not race each other. Never edit a migration that has already run elsewhere.