Laravel migrations are a way to manage database schema changes in a structured way. They allow you to create and modify database tables and their columns, as well as define indexes, constraints, and other database structures.
Here's how Laravel migrations work:
- Migration Files: Migrations in Laravel are stored as separate files in the database/migrations directory. Each migration file contains code to modify the database schema. The file name includes the timestamp when the migration was created, which ensures that they are executed in the correct order.
- Migration Class: Each migration file contains a migration class that extends the IlluminateDatabaseMigrationsMigration class. This class provides various methods and properties to define database schema changes.
- Up and Down Methods: Each migration class contains two primary methods: up() and down(). The up() method defines the changes to be made to the database schema, while the down() method specifies how to revert those changes.
- Schema Builder: To modify the database schema within migration classes, you can use Laravel's Schema Builder. It provides a fluent API to create tables, add columns or indexes, and apply constraints to the database schema.
- Running Migrations: To execute the migrations, you can use the migrate Artisan command. This command runs any pending migrations that haven't been executed yet. Larave can also track which migrations have been executed, preventing already executed migrations from running again.
- Rolling Back Migrations: If you need to reverse a migration, you can use the migrate:rollback Artisan command. By default, this command reverts the latest executed migration. You can also use the migrate:rollback command with the --step option to rollback multiple migrations.
Overall, Laravel migrations provide a simple and elegant way to manage database schema changes in a version-controlled manner. They make it easy and efficient to modify the database structure of your application as it evolves over time.