需要帮助理解一对一的Doctrine

Question

Referencing doctrine reference - one to many unidirectional

class User
{
  // ...

  /**
   * @ManyToMany(targetEntity="Phonenumber")
   * @JoinTable(name="users_phonenumbers",
   *      joinColumns={@JoinColumn(name="user_id", referencedColumnName="id")},
   *      inverseJoinColumns={@JoinColumn(name="phonenumber_id", referencedColumnName="id", unique=true)}
   *      )
   */
  private $phonenumbers;

  // ...
}

The part I don't understand is unique=true. What does it do? The way I read it is ...

• User has a Many to Many relationship with Phonenumber
• it uses the join table users_phonenumbers
• users_phonenumbers.user_id = users.id
• users_phonenumbers.phonenumber_id = Phonenumber.id
• and I guess the unique does something to constraints a many to many to a many to one relationship somehow. But how do you explain it? Also in a SQL sense (what is the output like)?

Answer 1

The mapping translates into the following SQL tables (assuming both have a surrogate ID, called id):

CREATE TABLE User (id INT(10) PRIMARY KEY)
CREATE TABLE Phonenumber (id INT(10) PRIMARY KEY)
CREATE TABLE User_Phonenumber (
  user_id INT(10),
  phonenumber_id INT(10),
  PRIMARY KEY (user_id, phonenumber_id),
  UNIQUE(phonenumber_id)
);

What this means in terms of your code:

$phonenumber = new Phonenumber();
$phonenumber->setNumber("123-4567890");
$user1->addPhonenumber($phonenumber);
$user2->addPhonenumber($phonenumber);
$entityManager->flush();

This would throw a unique constraint exception, you cannot add the same phonenumber to different users, because phonenumbers are unique (on the database level).