Yii2 - cannot add foreign key constraint

Question

I am coming from the Laravel world. I know that foreign keys are necessary for relations to work correctly. This is only my second day with the Yii2 framework.

I have set my primary indexes and foreign keys accordingly, as you can see in my code. I have two tables: A country table and a city table. A city can belong to a country, and a country has many cities:

Countries

use yii\db\Migration;

/**
 * Handles the creation of table `{{%countries}}`.
 */
class m190313_154240_create_countries_table extends Migration
{
    /**
     * {@inheritdoc}
     */
    public function safeUp()
    {
        $this->createTable('{{%countries}}', [
            'id' => $this->primaryKey(),
            'name' => $this->string(),

        ]);
        // add primary index
        $this->createIndex(
            '{{%idx-country_id}}',
            '{{%countries}}',
            'id'
        );
    }

    /**
     * {@inheritdoc}
     */
    public function safeDown()
    {
        $this->dropTable('{{%countries}}');
    }
}

Cities

use yii\db\Migration;

/**
 * Handles the creation of table `{{%cities}}`.
 * Has foreign keys to the tables:
 *
 * - `{{%country}}`
 */
class m190313_192616_create_cities_table extends Migration
{
    /**
     * {@inheritdoc}
     */
    public function safeUp()
    {
        $this->createTable('{{%cities}}', [
            'id' => $this->primaryKey(),
            'country_id' => $this->integer()->notNull(),
            'name' => $this->string('100')->notNull(),
        ]);

        // creates index for column `country_id`
        $this->createIndex(
            '{{%idx-cities-country_id}}',
            '{{%cities}}',
            'country_id'
        );

        // add foreign key for table `{{%country}}`
        $this->addForeignKey(
            '{{%fk-cities-country_id}}',
            '{{%cities}}',
            'country_id',
            '{{%country}}',
            'id',
            'CASCADE'
        );
    }

    /**
     * {@inheritdoc}
     */
    public function safeDown()
    {
        // drops foreign key for table `{{%country}}`
        $this->dropForeignKey(
            '{{%fk-cities-country_id}}',
            '{{%cities}}'
        );

        // drops index for column `country_id`
        $this->dropIndex(
            '{{%idx-cities-country_id}}',
            '{{%cities}}'
        );

        $this->dropTable('{{%cities}}');
    }
}

Yii2 does not appear to be as well documented as Laravel is. Google says I need to add primary keys. Did so, no luck. What am I missing?

Answer 1

Yii has nothing to do with your mistakes, Yii is awesome. The reason is you are providing incorrect table name in the cities migration while adding the foreign key

$this->addForeignKey(
'{{%fk-cities-country_id}}',
'{{%cities}}',
'country_id',
'{{%country}}',
'id',
'CASCADE'
);

You are creating the table with the name {{%countries}} , in the countries migration, whereas you have '{{%country}}' in the cities migration. Change it to '{{%countries}}' and it will work.

Note : you would need to drop the table cities before running the migration again.

Read More about Migrations Here