Migrations

Managing database schema with Migrations

graph TD A[Create Migration] --> B[Migration File] B --> C[up Method] B --> D[down Method] C --> E[Run Migration] E --> F[Schema Changes Applied] F --> G[Rollback if Needed] G --> D H[Migrations Table] --> I[Track Executed Migrations]

Migrations allow you to manage database schema with version control. This system allows you to apply database schema changes incrementally and reversibly.

Benefits of Using Migrations:

Version Control: All schema changes are stored in migration files
Team Collaboration: Team members can easily sync schema
Environment Consistency: Same schema across all environments (development, staging, production)
Rollback Support: Ability to rollback changes if needed
History Tracking: Complete history of schema changes
Automation: Automatic migration execution in deployment

Migration Structure:

Each migration file contains two methods:

<code>up()</code>: Changes that should be applied (create table, add column, etc.)
<code>down()</code>: Changes that should be rolled back (drop table, remove column, etc.)

Naming Conventions:

Migration files are prefixed with timestamp
Migration name should be descriptive
Use snake_case for migration name

Migration Types:

Create Table: Create new table
Alter Table: Modify existing table
Drop Table: Drop table
Add Column: Add column
Modify Column: Modify column
Drop Column: Drop column
Create Index: Create index
Drop Index: Drop index

Best Practices:

Each migration should perform one specific change
Use transactions for migrations
Commit migration files
Use descriptive names
Always implement down() method

Examples

Creating Migration

php artisan make:migration create_users_table
php artisan make:migration add_email_to_users_table --table=users
php artisan make:migration drop_users_table --table=users

Artisan commands to create different types of migrations.

Migration File - Create Table

<?php

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

return new class extends Migration
{
    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();
        });
    }
    
    public function down()
    {
        Schema::dropIfExists('users');
    }
};

A complete migration to create users table with all columns.

Migration - Add Column

<?php

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

return new class extends Migration
{
    public function up()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->string('phone')->nullable()->after('email');
            $table->boolean('is_active')->default(true);
            $table->index('email');
        });
    }
    
    public function down()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->dropColumn(['phone', 'is_active']);
            $table->dropIndex(['email']);
        });
    }
};

Adding new columns to existing table.

Migration - Foreign Keys

<?php

return new class extends Migration
{
    public function up()
    {
        Schema::table('posts', function (Blueprint $table) {
            $table->foreignId('user_id')
                ->constrained()
                ->onDelete('cascade');
            
            $table->foreignId('category_id')
                ->nullable()
                ->constrained()
                ->onDelete('set null');
        });
    }
    
    public function down()
    {
        Schema::table('posts', function (Blueprint $table) {
            $table->dropForeign(['user_id']);
            $table->dropForeign(['category_id']);
            $table->dropColumn(['user_id', 'category_id']);
        });
    }
};

Adding foreign keys with cascade and set null options.

Migration - Indexes

<?php

return new class extends Migration
{
    public function up()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->index('email');
            $table->unique('username');
            $table->index(['status', 'created_at']);
        });
    }
    
    public function down()
    {
        Schema::table('users', function (Blueprint $table) {
            $table->dropIndex(['email']);
            $table->dropUnique(['username']);
            $table->dropIndex(['status', 'created_at']);
        });
    }
};

Creating indexes to improve query performance.

Running Migrations

php artisan migrate
php artisan migrate:status
php artisan migrate:rollback
php artisan migrate:rollback --step=3
php artisan migrate:refresh
php artisan migrate:fresh
php artisan migrate:reset

Artisan commands to run and manage migrations.

Migration with Raw SQL

<?php

return new class extends Migration
{
    public function up()
    {
        DB::statement('ALTER TABLE users ADD FULLTEXT INDEX fulltext_name (name)');
    }
    
    public function down()
    {
        DB::statement('ALTER TABLE users DROP INDEX fulltext_name');
    }
};

Using raw SQL for complex operations not possible with Blueprint.

Use Cases

Managing schema changes in version control
Synchronizing database schema between environments
Rolling back schema changes if problems occur
Team collaboration for database changes
Automated deployment with schema updates
Tracking history of database changes

Common Mistakes

Forgetting to implement down() method
Creating migration with too many changes making rollback difficult
Not using transactions for migrations
Forgetting foreign keys in migrations
Not using indexes for performance
Modifying migration files that have already been run

Best Practices

Always implement down() method
Each migration should perform one specific change
Use descriptive names for migrations
Use transactions for migrations
Define foreign keys in migrations
Add indexes for frequently queried columns
Commit migration files and don't modify them

Edge Cases

Migrations with large datasets that may be slow
Migrations with data transformation
Migrations with multiple database connections
Migrations with custom database drivers
Rollback migrations with data loss
Migrations with conflicting changes

Performance Notes

Use indexes for frequently queried columns
Use batch operations for large data migrations
Use transactions for atomic operations
Use chunking for processing large datasets
Use raw queries for complex operations
Monitor migration execution time

Security Notes

Ensure migration files are in version control
Use raw SQL with caution
Ensure no sensitive data in migrations
Use environment variables for configuration
Ensure migrations are properly tested in production

Interview Points

What are migrations and why are they used?
What is the difference between migrate and migrate:fresh?
How can you rollback a migration?
Why should we implement down() method?
How can you add foreign key in migration?
What is the difference between migrate:refresh and migrate:reset?

Version Notes

Laravel 11.x: Improved performance in migration execution
Laravel 11.x: Better support for anonymous migrations
Laravel 10.x: Improved foreign key constraints
Laravel 9.x: Improved Blueprint API