m160209_063654_group_student__create_table.php

<?php

use yii\db\Migration;

class m160209_063654_group_student__create_table extends Migration
{
    public function up()
    {
        $this->createTable('{{%group_student}}', [
            'id' => $this->primaryKey(),
            'groupId' => $this->integer()->notNull(),
            'studentId' => $this->integer()->notNull(),
            'createdAt' => $this->dateTime(),
            'updatedAt' => $this->dateTime(),
        ]);
        $this->addForeignKey('FK_group_student_groupId', '{{%group_student}}', 'groupId', '{{%group}}', 'id');
        $this->addForeignKey('FK_group_student_studentId', '{{%group_student}}', 'studentId', '{{%user_account}}', 'id');
        $this->createIndex('UK_group_student_groupId_studentId', '{{%group_student}}', ['groupId', 'studentId'], true);
    }
    public function down()
    {
        $this->dropIndex('UK_group_student_groupId_studentId', '{{%group_student}}');
        $this->dropForeignKey('FK_group_student_studentId', '{{%group_student}}');
        $this->dropForeignKey('FK_group_student_groupId', '{{%group_student}}');
        $this->dropTable('{{%group_student}}');
    }
}