How to add foreign keys in Laravel Migration?

Web Development
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1

Hello, I am new to Laravel. I know I can use a migration to create a table. But I am having a hard time adding foreign keys and constraints.
I have a users table and I want the user id will be a foreign key in the posts table.

Schema::create('posts', function(Blueprint $table) {
    $table->increments('id'); 
    $table->bigInteger('user_id')->unsigned(); 
    $table->string('title', 255);
    $table->longText('content');
    $table->timestamps();
});

What’s the best way to add a foreign key?

2
  1. You have to make your user_id field an index:
    $table->index('user_id');
  1. Create a foreign key with constraint
    $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

Your migration should look like this

Schema::create('posts', function(Blueprint $table) {
    $table->increments('id'); 
    $table->bigInteger('user_id')->unsigned(); 
    $table->string('title', 255);
    $table->longText('content');
    $table->timestamps();
    $table->index('user_id');
    $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
});

In your down() function, you have to add those lines.

$table->dropForeign('lists_user_id_foreign');
$table->dropIndex('lists_user_id_index');
$table->dropColumn('user_id');
3

Why not use this?

    $table->dropForeign('user_id); 
    $table->dropIndex('user_id');