How to Write and Run Migrations with Diesel

Diesel migrations are managed via the diesel CLI tool, which generates, runs, and rolls back database schema changes. Install the CLI, generate a migration file, write your SQL, and run it against your database.

cargo install diesel_cli --no-default-features --features sqlite
mkdir -p src/migrations
# Generate a new migration named 'create_users'
diesel migration generate create_users
# Edit the up.sql and down.sql files in the new directory
# Run the migration
diesel migration run

The diesel migration generate command creates a timestamped directory with up.sql (to apply changes) and down.sql (to revert them). You write raw SQL in these files, then diesel migration run executes the up.sql scripts in order, tracking progress in a diesel_schema_migrations table.

Diesel migrations are a way to keep your database structure in sync with your code as it changes. Think of them like version control for your database schema: you write the steps to upgrade your database (and how to undo them) in simple text files. When you run the migration, Diesel applies these steps automatically, ensuring your database matches the current version of your application.