Why is creating Foreign Key in Laravel 5.8 failing?

Question

The migration script below was running smoothly in an older version of Laravel but I added it to my fresh Laravel 5.8 and ran the script. I\'m getting Error: foreign k

Answer 1

  update your `integer('user_id')` to `bigInteger('user_id')`
public function up() { 
        Schema::create('evaluation', function (Blueprint $table) { 
            $table->increments('id'); 
            $table->bigInteger('user_id')->unsigned()->index(); 
            $table->timestamps();
            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
        });
    }

Answer 2

As we discussed in the comments above, a foreign key column must be the same data type as the primary key it references.

You declared your user.id primary key as $table->bigIncrements('id') which becomes BIGINT UNSIGNED AUTO_INCREMENT in MySQL syntax.

You must declare the foreign key as $table->unsignedBigInteger('user_id') which will become BIGINT UNSIGNED in MySQL, making it compatible with being a foreign key to the user.id column.