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Laravel Database Migrations

From WikiOD

Inside a database migration[edit | edit source]

Each migration should have an up() method and a down() method. The purpose of the up() method is to perform the required operations to put the database schema in its new state, and the purpose of the down() method is to reverse any operations performed by the up() method. Ensuring that the down() method correctly reverses your operations is critical to being able to rollback database schema changes.

An example migration file may look like this:

<?php

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class AddLastLoggedInToUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->dateTime('last_logged_in')->nullable();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->dropColumn('last_logged_in');
        });
    }
}

When running this migration, Laravel will generate the following SQL to run against your database:

ALTER TABLE `users` ADD `last_logged_in` DATETIME NULL

Migrations[edit | edit source]

To control your database in Laravel is by using migrations. Create migration with artisan:

php artisan make:migration create_first_table --create=first_table

This will generate the class CreateFirstTable. Inside the up method you can create your columns:

<?php

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateFirstTable extends Migration
{
    public function up()
    {
        Schema::create('first_table', function (Blueprint $table) {
            $table->increments('id');
            $table->string('first_string_column_name');
            $table->integer('secont_integer_column_name');
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::drop('first_table');
    }
}

At the end to run all of your migrations classes you can run the artisan command:

php artisan migrate

This will create your tables and your columns in your database. Other useful migrate command are:

  • php artisan migrate:rollback - Rollback the last database migration
  • php artisan migrate:reset - Rollback all database migrations
  • php artisan migrate:refresh - Reset and re-run all migrations
  • php artisan migrate:status - Show the status of each migration

Modifying existing tables

Sometimes, you need to change your existing table structure like renaming/deleting columns. Which you can accomplish by creating a new migration.And In the up method of your migration.

//Renaming Column.

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

Above example will rename email column of users table to username. While the below code drops a column username from users table.

IMPROTANT : For modifying columns you need to add doctrine/dbal dependency to project's composer.json file and run composer update to reflect changes.

//Droping Column
public function up()
{
    Schema::table('users', function (Blueprint $table) {
        $table->dropColumn('username');
    });
}

Generating migration files[edit | edit source]

Creating a new migration file with the correct filename every time you need to change your schema would be a chore. Thankfully, Laravel's artisan command can generate the migration for you:

php artisan make:migration add_last_logged_in_to_users_table

You can also use the --table and --create flags with the above command. These are optional and just for convenience, and will insert the relevant boilerplate code into the migration file.

php artisan make:migration add_last_logged_in_to_users_table --table=users

php artisan make:migration create_logs_table --create=logs

You can specify a custom output path for the generated migration using the --path option. The path is relative to the application's base path.

php artisan make:migration --path=app/Modules/User/Migrations

The migration files[edit | edit source]

Migrations in a Laravel 5 application live in the database/migrations directory. Their filenames conform to a particular format:

<year>_<month>_<day>_<hour><minute><second>_<name>.php

One migration file should represent a schema update to solve a particular problem. For example:

2016_07_21_134310_add_last_logged_in_to_users_table.php

Database migrations are kept in chronological order so that Laravel knows in which order to execute them. Laravel will always execute migrations from oldest to newest.

Running migrations[edit | edit source]

Once your migration is written, running it will apply the operations to your database.

php artisan migrate

If all went well, you'll see an output similar to the below:

Migrated: 2016_07_21_134310_add_last_logged_in_to_users_table

Laravel is clever enough to know when you're running migrations in the production environment. If it detects that you're performing a destructive migration (for example, one that removes a column from a table), the php artisan migrate command will ask you for confirmation. In continuous delivery environments this may not be wanted. In that case, use the --force flag to skip the confirmation:

php artisan migrate --force

If you've only just run migrations, you may be confused to see the presence of a migrations table in your database. This table is what Laravel uses to keep track of what migrations have already been run. When issuing the migrate command, Laravel will determine what migrations have yet to run, and then execute them in chronological order, and then update the migrations table to suit.

You should never manually edit the migrations table unless you absolutely know what you're doing. It's very easy to inadvertently leave your database in a broken state where your migrations will fail.

Rolling Back Migrations[edit | edit source]

What if you want to rollback the latest migration i.e recent operation, you can use the awesome rollback command. But remember that this command rolls back only the last migration, which may include multiple migration files

php artisan migrate:rollback

If you are interested in rolling back all of your application migrations, you may use the following command

php artisan migrate:reset

Moreover if you are lazy like me and want to rollback and migrate with one command, you may use this command

php artisan migrate:refresh
php artisan migrate:refresh --seed

You can also specify number of steps to rollback with step option. Like this will rollback 1 step.

php artisan migrate:rollback --step=1

Credit:Stack_Overflow_Documentation