mysql - 如何修复运行迁移时外键错误

Question

我不知道为什么它仍然不起作用并显示:

Illuminate\Database\QueryException : SQLSTATE[HY000]: General error: 1005 Can't create table db_rocnikovka.books (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table books add constraint books_doba_foreign foreign key (doba) references druh_knihies (id_druhu))

at C:\xampp\htdocs\Rocnikovka\vendor\laravel\framework\src\Illuminate\Database\Connection.php:665

Exception trace: 1 PDOException::("SQLSTATE[HY000]: General error: 1005 Can't create > table db_rocnikovka.books (errno: 150 "Foreign key constraint is incorrectly formed")") C:\xampp\htdocs\Rocnikovka\vendor\laravel\framework\src\Illuminate\Database\Connection.php:459

2 PDOStatement::execute()

  C:\xampp\htdocs\Rocnikovka\vendor\laravel\framework\src\Illuminate\Database\Connection.php:459

 catch (Exception $e) {
    throw new QueryException(
       $query, $this->prepareBindings($bindings), $e
    );
 }

第一个表

class CreateDruhKnihiesTable extends Migration
{
    public function up()
    {
        Schema::create('druh_knihies', function (Blueprint $table) {
            $table->bigIncrements('id_druhu');
            $table->string('nazev');
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::dropIfExists('druh_knihies');
    }
}

第二个表

class CreateBooksTable extends Migration
{
    public function up()
    {
        Schema::create('books', function (Blueprint $table) {
            $table->bigIncrements('id_book');
            $table->string('nazev');
            $table->string('autor');
            $table->string('druh');
            $table->unsignedInteger('doba');
            $table->foreign('doba')->references('id_druhu')->on('druh_knihies');
            $table->integer('pocet_stranek');
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::dropIfExists('books');
    }
}

Answer 1

您的外键需要与其引用的键具有相同的类型。因此，第二个表外键 doba 需要更改为此，因为您在第一个表主键中使用了 BigIncrements()。

$table->unsignedBigInteger('doba');