1215一般错误：无法添加外键约束Laravel

Posted 2021-04-27

我有一个具有已创建外键约束的表：

错误：

 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)

这是联赛表

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();
    }

这是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();
            $table->string('current_stage_id')->nullable();
            AppHelpersDbExtender::defaultParams($table, true);
        });

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

        });

    }

我已经尝试过交换unSignedInteger，BigInteger，但它们似乎都不起作用。知道为什么会这样吗？谢谢

答案

正如@repat指出的，在两个表上都添加带有index（）的unSignedInteger对我来说很有效。

最终联赛表：

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();
    }

最终联赛季节表：

    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();
            $table->string('current_stage_id')->nullable();
            AppHelpersDbExtender::defaultParams($table, true);
        });

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

        });

    }

另一答案

要创建Foreign key，child column的数据类型必须与parent column完全匹配。例如，由于leagues.id是INT，所以league_seasons.league_id也需要是INT，而不是unsignedInteger。

因此改变

$table->unsignedInteger('league_id');

to

$table->integer('league_id');