title: How can I delete a child table row but keep its parent in Class Table Inheritance in doctrine orm 2?
body: <p>I have two entities, Item and SpecialItem</p>
  
  <p>SpecialItem extends Item, where Item is normal shopping item with price property, and the SpecialItem is a shopping item on sale with extra discount property.</p>
  
  <p>I'm using <a href="http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/inheritance-mapping.html#class-table-inheritance" rel="nofollow">Class Table Inheritance</a></p>
  
  <p>The Item: </p>
  
  <pre><code>&lt;?php
  
  namespace AppBundle\Entity;
  
  use Doctrine\ORM\Mapping as ORM;
  
  
  /**
   * Item
   *
   * @ORM\Table(name="item")
   * @ORM\Entity
   * @ORM\InheritanceType("JOINED")
   * @ORM\DiscriminatorColumn(name="item_type", type="string")
   * @ORM\DiscriminatorMap({"item" = "Item", "special" = "SpecialItem"})
   */
  
  class Item
  {
  /**
   * @var integer
   *
   * @ORM\Column(name="id", type="integer")
   * @ORM\Id
   * @ORM\GeneratedValue(strategy="IDENTITY")
   */
  private $id;
  
  /**
   * @var string
   *
   * @ORM\Column(name="title", type="string", length=255, nullable=false)
   */
  private $title;
  
  /**
   * @var string
   *
   * @ORM\Column(name="price", type="decimal", precision=10, scale=0, nullable=false)
   */
  private $price;
  
  /**
   * @var string
   *
   * @ORM\Column(name="description", type="text", length=65535, nullable=true)
   */
  private $description;
  
  
  }
  </code></pre>
  
  <p>The Special Item :</p>
  
  <pre><code>&lt;?php
  
  
   namespace AppBundle\Entity;
  
   use Doctrine\ORM\Mapping as ORM;
  
   /**
   * @ORM\Entity
   */
   class SpecialItem extends Item
   {
  
   /**
   * @var string
   *
   * @ORM\Column(name="discount", type="decimal", precision=10, scale=0,   nullable=false)
   */
   private $discount;
  
  
   }
  </code></pre>
  
  <p>If I created a SpecialItem and persisted it (now it has one row in table item and one row in table specialitem with discount value), and now I decided to remove the discount so the special item will now be a normal item. </p>
  
  <p>How can I remove the discount related rows only not the whole item and change the DiscriminatorColumn to reflect the parent type Item ?</p>