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Database Migrations & Seeding

Migrations are version control for database schemas. They allow a team to define, modify, and share database structure definitions across environments using PHP.

Generating Migrations

# Create a new table
php artisan make:migration create_posts_table

# Modify an existing table
php artisan make:migration add_status_to_posts_table --table=posts

Migration Structure

Migrations live in database/migrations/ and contain up() and down() methods:

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

return new class extends Migration
{
    public function up(): void
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->foreignId('user_id')->constrained()->cascadeOnDelete();
            $table->string('title');
            $table->string('slug')->unique();
            $table->text('body');
            $table->boolean('is_published')->default(false);
            $table->timestamp('published_at')->nullable();
            $table->timestamps();
            $table->softDeletes();
        });
    }

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

Common Column Types

Common Column Modifiers

$table->string('email')->nullable();           // Allows NULL values
$table->string('role')->default('subscriber'); // Default value
$table->string('username')->unique();          // Unique index
$table->string('category')->index();           // Standard index
$table->string('subtitle')->after('title');    // Place column after existing one (MySQL)

Foreign Key Constraints

Modern Laravel syntax uses concise foreign ID helpers:

// Shorthand for user_id referencing id on users table with cascade delete
$table->foreignId('user_id')->constrained()->cascadeOnDelete();

// Nullable foreign key that sets null on delete
$table->foreignId('category_id')->nullable()->constrained()->nullOnDelete();

// Manual foreign key definition
$table->unsignedBigInteger('author_id');
$table->foreign('author_id')->references('id')->on('users')->onDelete('cascade');

Modifying Existing Tables

When modifying an existing table, specify changes in up() and reverse them in down():

public function up(): void
{
    Schema::table('posts', function (Blueprint $table) {
        $table->string('subtitle')->nullable()->after('title');
        $table->renameColumn('body', 'content');
    });
}

public function down(): void
{
    Schema::table('posts', function (Blueprint $table) {
        $table->dropColumn('subtitle');
        $table->renameColumn('content', 'body');
    });
}

Seeders & Model Factories

Seeders populate database tables with dummy or initial data (e.g. admin accounts, lookups).

1. Generating Seeders & Factories

php artisan make:seeder PostSeeder
php artisan make:factory PostFactory --model=Post

2. Defining a Factory (database/factories/PostFactory.php)

namespace Database\Factories;

use App\Models\User;
use Illuminate\Database\Eloquent\Factories\Factory;

class PostFactory extends Factory
{
    public function definition(): array
    {
        return [
            'user_id' => User::factory(),
            'title' => fake()->sentence(),
            'slug' => fake()->unique()->slug(),
            'body' => fake()->paragraphs(3, true),
            'is_published' => fake()->boolean(80),
        ];
    }
}

3. Calling Seeders in database/seeders/DatabaseSeeder.php

namespace Database\Seeders;

use App\Models\User;
use App\Models\Post;
use Illuminate\Database\Seeder;

class DatabaseSeeder extends Seeder
{
    public function run(): void
    {
        // Create an explicit admin user
        User::factory()->create([
            'name' => 'Admin User',
            'email' => 'admin@example.com',
        ]);

        // Generate 20 dummy posts with related users
        Post::factory(20)->create();

        // Or invoke specific seeder classes
        $this->call([
            RoleSeeder::class,
        ]);
    }
}

Running Migrations & Seeders

# Run pending migrations
php artisan migrate

# Run database seeders
php artisan db:seed

# Run a specific seeder class
php artisan db:seed --class=PostSeeder

# Roll back the last batch of migrations
php artisan migrate:rollback

# Drop all tables, re-run all migrations, and run seeders
php artisan migrate:fresh --seed

[!TIP] php artisan migrate:fresh --seed is the most common command during local development to reset the database to a clean, populated state.

[!CAUTION] Avoid migrate:fresh in production environments as it completely wipes existing tables and records.