Learning about database migration in Laravel 5

This article introduces to you database migrations, one of the most powerful functions in the Laravel5 framework. This article introduces the steps and methods of database migration in detail. It is very practical and friends in need can refer to it.

Database migrations is one of laravel's most powerful features. Database migration can be understood as a version controller for the database.

Contains two migration files in the database/migrations directory, one to create the user table and one for user password reset.

In the migration file, the up method is used to create the data table, and the down method is used to roll back, that is, delete the data table.

Execute database migration

php artisan migrate
#输出
Migration table created successfully.
Migrated: 2014_10_12_000000_create_users_table
Migrated: 2014_10_12_100000_create_password_resets_table

Looking at the mysql database, you can see that three tables have been generated. The migratoins table is the migration record table, users and pasword_resets.

If there is a problem with the design, perform a database rollback

php artisan migrate:rollback
#输出
Rolled back: 2014_10_12_100000_create_password_resets_table
Rolled back: 2014_10_12_000000_create_users_table

Check the mysql database again, only the migrations table is left, and users password_resets has been deleted.

Modify the migration file and perform migration again.

New migration

php artisan make:migration create_article_table --create='articles'
#输出
Created Migration: 2015_03_28_050138_create_article_table

A new file is generated under database/migrations.

<?php

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

class CreateArticleTable extends Migration {

 /**
 * Run the migrations.
 *
 * @return void
 */
 public function up()
 {
 Schema::create(&#39;articles&#39;, function(Blueprint $table)
 {
  $table->increments(&#39;id&#39;);
  $table->timestamps();
 });
 }

 /**
 * Reverse the migrations.
 *
 * @return void
 */
 public function down()
 {
 Schema::drop(&#39;articles&#39;);
 }

}

The id column is automatically added and grows automatically. timestamps() will automatically generate two time columns: created_at and updated_at. Let’s add some fields:

 public function up()
 {
 Schema::create('articles', function(Blueprint $table)
 {
  $table->increments('id');
      $table->string('title');
      $table->text('body');
      $table->timestamp('published_at');
  $table->timestamps();
 });
 }

Execute the migration:

php artisan migrate

Now there is a new data table.

Suppose we need to add a new field, you can roll back, then modify the migration file, and perform the migration again, or you can directly create a new migration file

php artisan make:migration add_excerpt_to_articels_table

View the newly generated The migration file

<?php

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

class AddExcerptToArticelsTable extends Migration {

 /**
 * Run the migrations.
 *
 * @return void
 */
 public function up()
 {
 //
 }

 /**
 * Reverse the migrations.
 *
 * @return void
 */
 public function down()
 {
 //
 }

}

has only empty up and down methods. We can add the code manually, or we let Laravel generate the basic code for us. Delete this file, regenerate the migration file, and pay attention to adding parameters:

php artisan make:migration add_excerpt_to_articels_table --table='articles'

Now, there is initial code in the up method.

 public function up()
 {
 Schema::table('articles', function(Blueprint $table)
 {
  //
 });
 }

Add actual data modification code:

 public function up()
 {
 Schema::table('articles', function(Blueprint $table)
 {
  $table->text('excerpt')->nullable();
 });
 }
 
 public function down()
 {
 Schema::table('articles', function(Blueprint $table)
 {
  $table->dropColumn('excerpt');
 });
 }

nullable() represents the field Can also be empty.

Execute the migration again and check the database.

If we, just for fun, perform a rollback

php artisan migrate:rollback

excerpt column is gone.

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