Migrations in Laravel: Managing Database Schema Changes with Ease

Migration is a process of managing changes to your database schema over time. It allows you to create, update, and rollback database schema changes easily and reliably. In Laravel, migration is used to version control your database schema.

Creating a Migrations in Laravel

To create a new migration, you can use the make:migration Artisan command. For example, to create a migration for creating a new users table, you can run the following command:

php artisan make:migration create_users_table

This will create a new migration file in the database/migrations directory.

Migration Structure

A migration file contains two methods: up() and down(). The up() method is used to define the changes you want to make to your database schema, while the down() method is used to define how to undo those changes.

For example, to create a users table, you can define the schema changes in the up() method as follows:

public function up(){    Schema::create('users', function (Blueprint $table) {        $table->id();        $table->string('name');        $table->string('email')->unique();        $table->timestamp('email_verified_at')->nullable();        $table->string('password');        $table->rememberToken();        $table->timestamps();    });}

To rollback the users table creation, you can define the undo operations in the down() method as follows:

public function down(){    Schema::dropIfExists('users');}

Running Migration in Laravel

To run your migrations, you can use the migrate Artisan command. This will run all pending migrations:

php artisan migrate

You can also rollback the last batch of migrations using the rollback command:

php artisan migrate:rollback

for a partcular step rollback use this

php artisan migrate:rollback --step=2

Updating Migrations in Laravel

If you need to update an existing migration, you can use the migrate:rollback command to rollback the migration, then update the migration file, and run the migration again using the migrate command.

If we have the data in the table, then we can create a new migration and instead of create() use table() method to update the existing user’s table.

public function up(){    Schema::table('users', function (Blueprint $table) {        $table->string('role');    });}

Here we added the role column in the users table.

Foreign Key Constraints in Laravel

You can add foreign key constraints to your migration using the foreign() method. For example, to add a foreign key constraint to the users table that references the roles table, you can define the foreign key in the up() method as follows:

public function up(){    Schema::create('users', function (Blueprint $table) {        $table->id();        $table->string('name');        $table->unsignedBigInteger('role_id');        $table->foreign('role_id')->references('id')->on('roles');        $table->timestamps();    });}

Adding and Removing Database Indexes

You can add or remove database indexes using the index() and dropIndex() methods. For example, to add a unique index on the email column of the users table, you can define the index in the up() method as follows:

public function up(){    Schema::table('users', function (Blueprint $table) {        $table->unique('email');    });}

To remove the unique index, you can define the dropIndex() method in the down() method as follows:

public function down(){    Schema::table('users', function (Blueprint $table) {        $table->dropIndex('users_email_unique');    });}

Conclusion

In Laravel, migration is a powerful tool for managing your database schema. You can create, update, and rollback migrations easily using Artisan commands. You can also add foreign key constraints and add or remove database indexes using the foreign() and index() methods respectively. By version controlling your database schema with migrations, you can easily collaborate with other developers and deploy your application with confidence.

In summary, to use migrations in Laravel, you need to create migration files using the make:migration Artisan command, define the schema changes in the up() method, define the undo operations in the down() method, run migrations using the migrate command, and rollback migrations using the rollback command. Additionally, you can add foreign key constraints and database indexes using the foreign() and index() methods respectively.