symfony2 Doctrine 关联删除问题

Entity NotifyOrderCreate

/**
 * @ORM\Column(type="bigint",options={"unsigned"=true})
 * @ORM\Id
 * @ORM\GeneratedValue(strategy="AUTO")
 */
private $id;

/**
 * @ORM\OneToOne(targetEntity="Order", inversedBy="notifyCreate",cascade={"persist"})
 * @ORM\JoinColumn(name="order_id", referencedColumnName="id",onDelete="CASCADE")
 **/
private $order;

Entity Order

/**
 * @ORM\Column(type="bigint",options={"unsigned"=true})
 * @ORM\Id
 * @ORM\GeneratedValue(strategy="AUTO")
 */
private $id;

/**
 * @ORM\OneToOne(targetEntity="NotifyOrderCreate", mappedBy="order")
 **/
private $notifyCreate;

查找出NotifyOrderCreate 执行remove的时候会把order也删除掉，求怎么破。

---

我不了解注释写法。下面给出的是yml代码：

oneToOne:
    order:
        targetEntity: SomeEntity
        joinColumn:
            name: some_id
            referencedColumnName: pk_id
            nullable: true
            onDelete: SET NULL

这种写法会在删除时把字段设置为NULL。