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Lam Hoang
Lam Hoang

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Laravel Cheat Sheet - Migrations

Migrations problems

The limit for keys is 767 bytes.

In the utf-8 encoding, the single character is 3 bytes, so key on VARCHAR(255) length won't exceed 767 (3 * 255 = 765).

In you are using utf8mb4, which we are, the single character is 4 bytes. Thus the maximum length for VARCHAR which has key on it (like UNIQUE) is 191.

When you encounter this:

Migration table created successfully.
Migrating: 2014_10_12_000000_create_users_table

Illuminate\Database\QueryException  : SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes (SQL: alter table `users` add unique `users_email_unique`(`email`))

Change the email field length to 191.

Running migrations

To run the most recent, not executed yet migrations

php artisan migrate

To rollback the most recent migration

php artisan migrate:rollback

Setting the length of the field

$table->string('email', 191);

Writing migrations

Creating a new migration

php artisan make:migration create_blogposts_table

To prefill the migration with stub code that creates a new table

php artisan make:migration create_blogposts_table --create=blogposts

To prefill the migration with stub code that modifies an existing table

php artisan make:migration add_date_to_blogposts_table --table=blogposts

The migration file

Migration file containts a class with 2 methods, up() and down()

The up() methods creates new table, modifies the existing one. Generally, it specifies how your database schema should change from now on - this might include deleting fields or tables.

The down() method specifies how to revert changes made my migration.

up() method is called when you run php artisan migrate

down() method is called when you run php artisan migrate:rollback

Creating a new table

Schema::create('blogposts', function (Blueprint $table) {

Renaming an existing table

Schema::rename('blogposts', 'posts');

Creating columns

Schema::table('blogposts', function (Blueprint $table) {

Available column types

Refer to this link

Typical columns types

Command Description
$table->increments('id'); Auto-incrementing UNSIGNED INTEGER
$table->string('title', 100); VARCHAR with optional length
$table->timestamps(); Nullable TIMESTAMP created_at and updated_at columns
$table->text('content'); TEXT

Column modifiers

->default('value') - the default column value

->nullable() - column can be NULL

->unsigned() - integer is unsigned (no negative values)

Source: Laravel Cheat Sheet

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