I can't add foreign key constraint in Laravel-CodePudding

I'm working on small chat application using Laravel, I'm getting a migration error:

this is my migration :

Schema::create('chats', function (Blueprint $table) {
            $table->id();

            $table->integer('from_id');
            $table->integer('to_id');
            $table->text('message');

            $table->foreign('from_id')->references('id')->on('users');
            $table->foreign('to_id')->references('id')->on('users');

            $table->timestamps();
        });

Error :

 SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL: alter table `chats` add constraint `chats_from_id_foreign` foreign key (`from_id`) references `users` (`id`))

I refreshed and I recreate my database, but still have the same error

CodePudding user response：

As mentioned in the comment, the reference key must have the same column type. But laravel has foreignId() method that same as default id type. For laravel 6 , the default id type is unsigned big integer, before laravel 6, the default id has unsigned integer type.

so you need to change

$table->integer('from_id');
$table->integer('to_id');

$table->foreignId('from_id');
$table->foreignId('to_id');

Another alternative way, just use foreignIdFor() method to create column and add foreign key in single line.

$table->foreignIdFor(\App\Models\User::class,'from_id')->constrained()->cascadeOnDelete();
$table->foreignIdFor(\App\Models\User::class,'to_id')->constrained()->cascadeOnDelete();

CodePudding user response：

You must follow the same datatype with unsigned for foreign key. By default laravel uses bigint so you must use unsignedBigInteger

Schema::create('chats', function (Blueprint $table) {
            $table->id();

            $table->unsignedBigInteger('from_id');
            $table->unsignedBigInteger('to_id');
            $table->text('message');

            $table->foreign('from_id')->references('id')->on('users');
            $table->foreign('to_id')->references('id')->on('users');

            $table->timestamps();
        });