query.java

 //  get all components belonging to a rack
    @Query("SELECT c.id, cc.name as category_name, c.rack_id, c.component_category_id, c.name, c.img_path, c.code, " +
            "       (SELECT COUNT(c.name) " +
            "        FROM rack r " +
            "        WHERE c.rack_id = : rackID ) as count " +
            "FROM component c " +
            "INNER JOIN component_category cc ON cc.id = c.component_category_id " +
            "WHERE c.rack_id = :rackID and cc.id = c.component_category_id " +
            "ORDER BY c.name ASC")
    LiveData<List<Component>> getRackComponents(long rackID);