title: Not able to get query results using Room persistence
body: <p>I am developing an Android app using the Room persistence library. I have a User and a Car entity</p>
  
  <pre><code>@Entity(tableName = "users")
  public class User {
  
      @PrimaryKey
      @NonNull
      private int id;
      private String name;
  
      public User(@NonNull int id, String name) {
          this.id = id;
          this.name = name;
      }
  }
  </code></pre>
  
  <p>and</p>
  
  <pre><code>@Entity(tableName = "cars", foreignKeys = @ForeignKey(parentColumns  = 
  "id", childColumns = "userId", entity = User.class))
  public class Car {
  
      @PrimaryKey(autoGenerate = true)
      private int id;
      private int userId;
      private String brand;
  
      public Car(int userId, String brand) {
          this.userId = userId;
          this.brand = brand;
      }
  }
  </code></pre>
  
  <p>Also I have created a UserWithCar class as below:</p>
  
  <pre><code>public class UserWithCar {
  
      @Embedded(prefix = "user_")
      public User user;
  
      @Embedded(prefix = "car_")
      public Car car;
  }
  </code></pre>
  
  <p>As you can see in the UserWithCar I use a prefix cause if I don't I get the following error: </p>
  
  <blockquote>
    <p>Multiple fields have the same columnName: id. Field names: user > id,
    car > id.</p>
  </blockquote>
  
  <p>I want to get all the UserWithCar using the following query:</p>
  
  <pre><code>@Query("SELECT * FROM users JOIN cars ON users.id = cars.userId")
  List&lt;UserWithCar&gt; getUserWithCar();
  </code></pre>
  
  <p>Using this query I get the following error:</p>
  
  <blockquote>
    <p>The query returns some columns [id, name, id, userId, brand] which are
    not use by com.roomdemo.data.models.UserWithCar. You can use
    @ColumnInfo annotation on the fields to specify the mapping.
    com.roomdemo.data.models.UserWithCar has some fields [user_id,
    user_name, car_id, car_userId, car_brand] which are not returned by
    the query. If they are not supposed to be read from the result, you
    can mark them with @Ignore annotation. You can suppress this warning
    by annotating the method with
    @SuppressWarnings(RoomWarnings.CURSOR_MISMATCH). Columns returned by
    the query: id, name, id, userId, brand. Fields in
    com.foodtec.roomdemo.data.models.UserWithCar: user_id, user_name,
    car_id, car_userId, car_brand.</p>
  </blockquote>
  
  <p>Can I have some help? Thanks!</p>
  
  <p><strong>Update</strong> 
  Using @Wizard help, I removed the prefix from the @Embeded and I added @ColumnInfo "uId" for the User's id and "cId for the Car's id in order to not have the same id field. By this way it works! </p>