运行 迁移时如何修复外键错误

Question

我不知道为什么它仍然不起作用并显示这个：

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table

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table

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 table 外键 doba 需要更改为此，因为您在第一个 table 主键中使用 BigIncrements()。

$table->unsignedBigInteger('doba');

Answer 2

这里的问题是 druh_knihies 中的 id_druhu 被定义为 bigIncrements 而你创建 doba 为 unsignedInteger 并且在使用外键类型时应该完全一样。所以在这种情况下而不是

$table->unsignedInteger('doba');

你应该使用

$table->unsignedBigInteger('doba');