Android Room Dao，获得空值

Question

这是Room Db Dao设置，我用于存储和检索数据。有人帮我告诉我，这里有没有鱼。运行getUser()时得到空值。我只有一个用户来保存更新和检索。

@Dao
interface UserDao {

  @Insert(onConflict = OnConflictStrategy.REPLACE)
  fun insert(userEntity: UserEntity): Long

  @Update
  fun update(userEntity: UserEntity): Int

  @SuppressWarnings(RoomWarnings.CURSOR_MISMATCH)
  @Query("SELECT 'first',* FROM usertable ORDER BY id DESC" )
  fun getUser(): UserEntity

  @Query("DELETE from usertable")
  fun remUser(): Int
}

谢谢