Cannot add foreign key constraint in Laravel Migrations

Question

I currently have two tables Symbols and Prices . I am currently creating a migration for Prices and adding a FK constraint to Prices.symbol_id which references Symbols.id . This is the Prices migration:

        $table->increments('id');
        ...
        ...
        $table->integer('symbol_id');
        $table->foreign('symbol_id')
            ->references('id')->on('Symbols')
            ->onDelete('cascade’);

Symbols.id is simply a $table->increments('id');

However, when I run the migration, this is what happens:

  [Illuminate\Database\QueryException]                                                 
  SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL: alter   
  table `Prices` add constraint prices_symbol_id_foreign foreign key (`symbol_id`) re  
  ferences `Symbols` (`id`))                  

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

Any ideas why?

Answer 1

make a new migration

php artisan make:migration update_prices_table

The schema:

 public function up()
 {
    Schema::table('Prices', function (Blueprint $table) {
        $table->integer('symbol_id)->unsigned();
        $table->foreign('symbol_id')
        ->references('id')->on('Symbols')
        ->onDelete('cascade’);
    });
}

Answer 2

如果您的主键类型为bigIncrements ，请确保将bigInteger用作外键的数据类型