Integrity constraint violation: 1452 Cannot add or update a child row:

Question

I am trying to insert values into my comments table and I am getting a error. Its saying that I can not add or update child row and I have no idea what that means.

m

Answer 1

that means that the value for column project_id on table comments you are inserting not only doesn't exist on table projects BUT also project_id probably doesn't have default value. E.g. in my case I set it as NULL.

As for Laravel you can consider this expressions as a chunk of code of a migration php file, for example:

class ForeinToPhotosFromUsers extends Migration

{ /** * Run the migrations. * * @return void */

public function up()
{
    Schema::table('users', function (Blueprint $table) {
    $table->unsignedBigInteger('photo_id')->nullable();// ! ! ! THIS STRING ! ! !
    $table->foreign('photo_id')->references('id')->on('photos');
});
}

}

Obviously you had to create the Model class(in my case it was Photo) next to all these.