Laravel在迁移文件上添加外键

Question

i have this structure on card_price table in database:

CREATE TABLE IF NOT EXISTS `card_price` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `card_price` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `user_id` tinyint(3) unsigned NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

and this structure for users:

CREATE TABLE IF NOT EXISTS `users` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(20) COLLATE utf8_unicode_ci NOT NULL,
  `family` varchar(25) COLLATE utf8_unicode_ci NOT NULL,
  `username` varchar(15) COLLATE utf8_unicode_ci NOT NULL,
  `password` varchar(64) COLLATE utf8_unicode_ci NOT NULL,
  `email` varchar(20) COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

i'm creating this tables with migration files such as:

card_price:

Schema::create('card_price',function(Blueprint $table){
    $table->increments('id');
    $table->string('card_price');
    $table->tinyInteger('user_id')->unsigned();
    $table->foreign('user_id')->references('id')->on('users');
    $table->timestamps();
});

and users:

Schema::create('users', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name','20');
    $table->string('family','25');
    $table->string('username','15');
    $table->string('password','64');
    $table->string('email','20');
    $table->string('remember_token','100');
    $table->timestamps();
});

with this migration files i'm trying to create foreign key with user_id on card_price table and id on users table. unfortunately i get this error:

  [Illuminate\Database\QueryException]
  SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL
  : alter table `card_price` add constraint card_price_user_id_foreign foreig
  n key (`user_id`) references `users` (`id`))

  [PDOException]
  SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint

Answer 1

You are getting this error because of data type mismatch in foreign table. You should use same data type for parent and child table table column referencing it.

Change data type of user_id in card_price table to INT UNSIGNED NOT NULL;

First Alter your table with following query:

ALTER TABLE `card_price` 
CHANGE COLUMN `user_id` `user_id` INT UNSIGNED NOT NULL ;

query for foreign key reference:

ALTER TABLE `card_price` 
ADD CONSTRAINT `fk_users`
  FOREIGN KEY (`user_id`)
  REFERENCES `users` (`id`)
  ON DELETE NO ACTION
  ON UPDATE NO ACTION;