How to define foreign keys in migrations? - laravel

Question

The Problem
I want to add foreign keys to tables. When I run my first migration create_posts_table that looks like this:
Schema::create('posts', function(Blueprint $table) {
$table->engine = 'InnoDB';
$table->increments('id');
$table->unsignedInteger('user_id')->index();
// . . .
});
Schema::table('posts', function(Blueprint $table)
{
$table->foreign('user_id')->references('id')
->on('users')->onDelete('cascade');
});
The following error is thrown:
[Illuminate\Database\QueryException] SQLSTATE[HY000]:
General error: 1215 Cannot add foreign key constraint (SQL: alter table
posts add constraint posts_user_id_foreign foreign key (user_id) references users (id) on delete cascade)
This is caused because the users table is not created yet, hence the failure to create the users' referencing foreign key on the posts table.
Possible Solution
The solution to this problem would be to add the foreign keys with a new migration after all of the tables had been created. However, it seems clunky to me.
The question
How can I define the foreign keys inside their respective tables' migrations, instead of adding them separately with the different migration after all of the tables had been created?

Answer 1

You can perform multiple migrations in the same migration file. If you have a posts table where you want a foreign key to the users table, but the users table does not yet exist, you either have to do it in the users table migration file after the users table has been created - or you have to do a separate migration, like you said. You can't "save" instructions for later in migrations.

Answer 2

In laravel way is keeping separate migration files for different tables with indexing, primary key & foreign keys.....
CreateUsersTable
class CreateUsersTable extends Migration
{
public function up()
{
Schema::create('users', function (Blueprint $table) {
$table->increments('id');
$table->string('email');
$table->string('password', 60);
$table->enum('status', ['0', '1'])->default('0');
$table->rememberToken();
$table->nullableTimestamps();
$table->unique('email');
});
}
public function down()
{
Schema::drop('users');
}
}
CreatePostsTable
class CreatePostsTable extends Migration
{
public function up()
{
Schema::create('posts', function (Blueprint $table) {
$table->increments('id');
$table->integer('user_id')->unsigned();
$table->foreign('user_id')->references('id')->on('users');
});
}
public function down()
{
Schema::drop('posts');
}
}