Laravel migration: "Foreign key constraint is incorrectly formed" (errno 150)

Question

When migrating my DB, this error appears. Below is my code followed by the error that I am getting when trying to run the migration.

Code

public function up() {     Schema::create('meals', function (Blueprint $table) {         $table->increments('id');         $table->integer('user_id')->unsigned();         $table->integer('category_id')->unsigned();         $table->string('title');         $table->string('body');         $table->string('meal_av');         $table->timestamps();         $table->foreign('user_id')             ->references('id')             ->on('users')             ->onDelete('cascade');         $table->foreign('category_id')             ->references('id')             ->on('categories')             ->onDelete('cascade');     }); }   

Error message

[Illuminate\Database\QueryException]
SQLSTATE[HY000]: General error: 1005 Can't create table meal.#sql-11d2_1 4 (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter
table meals add constraint meals_category_id_foreign foreign key (category_id) references categories (id) on delete cascade)

Answer 1

When creating a new table in Laravel. A migration will be generated like:

$table->bigIncrements('id'); 

Instead of (in older Laravel versions):

$table->increments('id'); 

When using bigIncrements the foreign key expects a bigInteger instead of an integer. So your code will look like this:

public function up()     {         Schema::create('meals', function (Blueprint $table) {             $table->increments('id');             $table->unsignedBigInteger('user_id'); //changed this line             $table->unsignedBigInteger('category_id'); //changed this line             $table->string('title');             $table->string('body');             $table->string('meal_av');             $table->timestamps();              $table->foreign('user_id')                 ->references('id')                 ->on('users')                 ->onDelete('cascade');              $table->foreign('category_id')                 ->references('id')                 ->on('categories')                 ->onDelete('cascade');         });     }   

You could also use increments instead of bigIncrements like Kiko Sejio said.

The difference between Integer and BigInteger is the size:

• int => 32-bit
• bigint => 64-bit

Answer 2

@JuanBonnett’s question has inspired me to find the answer. I used Laravel to automate the process without considering the creation time of the file itself. According to the workflow, “meals” will be created before the other table (categories) because I created its schema file (meals) before categories. That was my fault.