title: Database FAIL - The database schema is not in sync with the current mapping file
body: <p>Can anybody explain the following doctrine schema validation error message please:</p>
  
  <p><img src="https://i.stack.imgur.com/2n5SB.png" alt="The error message returned by the schema validate function"></p>
  
  <p>Here is the the yaml ORM definition of each entity in the manyToMany relationship, created inline with section 5.9 of the <a href="http://docs.doctrine-project.org/en/latest/reference/association-mapping.html">documentation</a>.</p>
  
  <pre><code>Rep\Bundle\ProjectBundle\Entity\User:
      type: entity
      table: User
      fields:
          id:
              id: true
              type: integer
              unsigned: true
              nullable: false
              generator:
                  strategy: AUTO
          username:
              type: string
              length: 25
              fixed: false
              nullable: false
          salt:
              type: string
              length: 32
              fixed: false
              nullable: false
          password:
              type: string
              length: 40
              fixed: false
              nullable: false
          email:
              type: string
              length: 60
              fixed: false
              nullable: false
      manyToMany:
          roles:
              targetEntity: UserRole
              inversedBy: users
              joinTable:
                  name: UserRoleLookup
                  joinColumns:
                      user_id:
                          referencedColumnName: id
                  inverseJoinColumns:
                      user_role_id:
                          referencedColumnName: id
      lifecycleCallbacks: {  }
  </code></pre>
  
  <p>And the UserRole inverse yaml configuration:</p>
  
  <pre><code>Rep\Bundle\ProjectBundle\Entity\UserRole:
      type: entity
      table: UserRole
      fields:
          id:
              id: true
              type: integer
              unsigned: true
              nullable: false
              generator:
                  strategy: AUTO
          name:
              type: string
              length: 50
              fixed: false
              nullable: false
      manyToMany:
          users:
              targetEntity: User
              mappedBy: roles
      lifecycleCallbacks: {  }
  </code></pre>
  
  <p>Here is the User table schema:</p>
  
  <pre><code>CREATE TABLE `User` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `username` varchar(25) COLLATE utf8_unicode_ci NOT NULL,
    `salt` varchar(32) COLLATE utf8_unicode_ci NOT NULL,
    `password` varchar(40) COLLATE utf8_unicode_ci NOT NULL,
    `email` varchar(60) COLLATE utf8_unicode_ci NOT NULL,
    PRIMARY KEY (`id`)
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
  </code></pre>
  
  <p>The UserRole table schema:</p>
  
  <pre><code>CREATE TABLE `UserRole` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `name` varchar(50) COLLATE utf8_unicode_ci NOT NULL,
    PRIMARY KEY (`id`)
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
  </code></pre>
  
  <p>And the UserRoleLookup schema:</p>
  
  <pre><code>CREATE TABLE `UserRoleLookup` (
    `user_id` int(11) unsigned NOT NULL,
    `user_role_id` int(11) unsigned NOT NULL,
    PRIMARY KEY (`user_id`,`user_role_id`),
    KEY `user_role_id` (`user_role_id`),
    CONSTRAINT `userrolelookup_ibfk_2` FOREIGN KEY (`user_role_id`) REFERENCES `userrole` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
    CONSTRAINT `userrolelookup_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
  </code></pre>
  
  <p>As you can see, it's a pretty simplistic setup with a look-up table to dictate a user's roles or the set of users in a given user role. However, I'm receiving this frustrating synch error. I've read nothing here or online which answers this question in any concise detail, I was hoping someone could clarify if I am safe to leave this configuration and ignore this error?</p>