1215 一般錯誤：無法添加外鍵約束 Laravel

Question

我有一個已創建外鍵約束的表：

錯誤：

 SQLSTATE[HY000]: General error: 1215 Cannot add foreign key 
constraint (SQL: alter table `league_seasons` add 
constraint `league_seasons_league_id_foreign` foreign key (`league_id`)
 references `leagues` (`id`) on delete cascade)

這是排行榜

public function up() {
        Schema::create('leagues', function (Blueprint $table) {
            $table->integer('id');
            $table->increments('increment_id');
            $table->string('type')->nullable();
            $table->integer('legacy_id')->nullable();
            $table->integer('country_id')->nullable();
    }

這是 League_seasons 表

    public function up() {
        Schema::create('league_seasons', function (Blueprint $table) {
            $table->integer('id');
            $table->increments('increment_id');
            $table->string('name')->nullable();
            $table->unsignedInteger('league_id');
            $table->string('is_current_season')->nullable();
            $table->string('current_round_id')->nullable();
            $table->string('current_stage_id')->nullable();
            App\Helpers\DbExtender::defaultParams($table, true);
        });

        Schema::table('league_seasons', function (Blueprint $table) {
            $table->foreign('league_id')->references('id')->on('leagues')->onDelete('cascade');

        });

    }

我試過交換 unSignedInteger、BigInteger 但它們似乎都沒有工作。 知道為什么會這樣嗎？ 謝謝

Answer 1

正如@repat 指出的那樣，在兩個表上添加 unSignedInteger 和 index() 對我有用。

最終聯賽表：

public function up() {
        Schema::create('leagues', function (Blueprint $table) {
            $table->unsignedInteger('id')->index();
            $table->increments('increment_id');
            $table->string('type')->nullable();
            $table->integer('legacy_id')->nullable();
            $table->integer('country_id')->nullable();
            $table->string('name')->nullable();
    }

最終的 League_seasons 表：

    public function up() {
        Schema::create('league_seasons', function (Blueprint $table) {
            $table->integer('id');
            $table->increments('increment_id');
            $table->string('name')->nullable();
            $table->unsignedInteger('league_id')->index();
            $table->string('is_current_season')->nullable();
            $table->string('current_round_id')->nullable();
            $table->string('current_stage_id')->nullable();
            App\Helpers\DbExtender::defaultParams($table, true);
        });

        Schema::table('league_seasons', function (Blueprint $table) {
            $table->foreign('league_id')->references('id')->on('leagues')->onDelete('cascade');

        });

    }

Answer 2

要創建Foreign key ， child column的數據類型必須與parent column完全匹配。 例如，因為leagues.id是一個integer ， league_seasons.league_id也需要是一個integer ，而不是一個unsignedInteger integer 。

所以改變

$table->unsignedInteger('league_id');

到

$table->integer('league_id');