How much memory is used by each database in SQL Server?

SELECT
    CASE WHEN database_id = 32767 THEN 'Resource DB' ELSE DB_NAME (database_id) END AS 'DBName',
    COUNT (1) AS 'Page Count',
    (COUNT (1) * 8)/1024 AS 'Memory Used in MB' ,   
   CASE WHEN is_modified = 1 THEN 'Dirty Page' ELSE 'Clean Page' END AS 'Page State' 
FROM sys.dm_os_buffer_descriptors
   GROUP BY [database_id], [is_modified]
   ORDER BY   db_name(database_id)
GO