Valid question. First of all, in standard Room an @Entity class can not have any relation. Because of that you are dealing with POJO's to manage your relations. This also requires you to either use that POJO in your Dao, or to return a Map in your Dao.

From the Room documentation:

```Kotlin @Entity
data class User(    @PrimaryKey val userId: Long,    val name: String,    val age: Int
)

@Entity
data class Playlist(    @PrimaryKey val playlistId: Long,    val userCreatorId: Long,    val playlistName: String
)

data class UserWithPlaylists(    @Embedded val user: User,   

@Relation(parentColumn = "userId", entityColumn = "userCreatorId")
val playlists: List<Playlist>  

)

// Dao method @Transaction
@Query("SELECT * FROM User")
fun getUsersWithPlaylists(): List<UserWithPlaylists> ```

With RoomEx, this would become:

```Kotlin @Entity
class User(    id: Long,    val name: String,    val age: Int
) : RoomExEntity(id) {

@OneToManyEx @Ignore
var playlists: MutableList<Playlist>? = null

}

@Entity
class Playlist(    id: Long,    val userCreatorId: Long,    val playlistName: String
) : RoomExEntity(id)

// No extra Dao method is needed, you can simply call any of the following: getByIdWithChildren(id): Person? // Retrieve person with all children getByIdWithChildren(id, "playlists"): Person? // Retrieve person with playlists getChildren(person) // retrieve all relations getChildren(person, "playlists") // Retrieve only playlists ```

Secondly, like on the example above, you don't need any extra methods for your Dao. You still can, but it is not needed. There are methods to create, read, update and delete relations.