Version 2.1.0 and higher of the Room persistence library provides support for SQLite database views, allowing you to encapsulate a query into a class. Room refers to these query-backed classes as views, and they behave the same as simple data objects when used in a DAO.
Create a view
To create a view, add the @DatabaseView annotation to a class. Set the annotation's value to the query that the class should represent.
The following code snippet provides an example of a view:
Kotlin
@DatabaseView("SELECT user.id, user.name, user.departmentId," + "department.name AS departmentName FROM user " + "INNER JOIN department ON user.departmentId = department.id") data class UserDetail( val id: Long, val name: String?, val departmentId: Long, val departmentName: String? )
Java
@DatabaseView("SELECT user.id, user.name, user.departmentId," + "department.name AS departmentName FROM user " + "INNER JOIN department ON user.departmentId = department.id") public class UserDetail { public long id; public String name; public long departmentId; public String departmentName; }
Associate a view with your database
To include this view as part of your app's database, include the views property in your app's @Database annotation:
Kotlin
@Database(entities = [User::class], views =[UserDetail::class], version = 1) abstract class AppDatabase : RoomDatabase() { abstract fun userDao(): UserDao }
Java
@Database(entities = {User.class}, views = {UserDetail.class}, version = 1) public abstract class AppDatabase extends RoomDatabase { public abstract UserDao userDao(); }