OnDelete=CASCADE;
in this example only brands_notifications table will be clean from notification. Since from DB side we have 3 tables. It's impossible to change also notification table. so this REFERENTIAL ACTION influences only described table
class Brand
{
/**
* One Brand have Many Notifications - Unidirectional
*
* @ORM\ManyToMany(targetEntity="AppBundle\Entity\Notification", cascade={"persist", "remove"}, orphanRemoval=true)
* @ORM\JoinTable(name="brands_notifications",
* joinColumns={@ORM\JoinColumn(onDelete="CASCADE", name="brand_id", referencedColumnName="id")},
* inverseJoinColumns={@ORM\JoinColumn(onDelete="CASCADE", name="notification_id", referencedColumnName="id", unique=true)}
* )
*/
private $notifications;
}