Database Migrations

• Introduction
• Creating a Migration
• Migration Structure
• Running Migrations
  • Rolling Back Migrations

Introduction

Migrations allow you to easily create and share your database schema with others and make it easy to keep your database structure in sync. Think of it like version control for you database schema.

Creating a Migration

To create migration you can use the severell-cli tool to easy scaffold one. First to access the CLI tool you need to run

mvn severell:cli

This will start the Severell cli tool and from there you can create your first migration.

make:migration create_posts_table -c posts

The -c option means you want to create a new table called posts instead of modifying an existing table. Use the -t option to modify a table.

Migration Structure

Migrations are stored in out db folder in the root of your project. They contain 2 methods. The up and down methods.

package migrations;

import com.severell.core.database.migrations.Blueprint;
import com.severell.core.database.migrations.MigrationException;
import com.severell.core.database.migrations.Schema;

public class CreateUsersTable {

    public static void up() throws MigrationException {
        Schema.create("users", (Blueprint table) -> {
            table.id();
            table.string("name");
            table.string("email");
            table.string("password");
            table.timestamp("verified_at").nullable();
            table.timestamps();
        });
    }

    public static void down() throws MigrationException {
        Schema.drop("users");
    }

}

Running Migrations

To run migrations you can use the following command in the Severell cli tool.

migrate

Since migrations only run one time the next time you run severell-cli migrate it will not run the same migrations again. It will only run all outstanding migrations.

Rolling Back Migrations

If you need to rollback your last migration you can use the migrate:rollback command.

migrate:rollback

This will rollback your last migration run. So it could include a number of migrations. If you want to rollback all your migrations you can use the migrate:reset command.

migrate:reset