How to check used memory by DB

How to check used memory by DB

Sometimes the ireports are loading slowly the possible issue is memory usage from DB, below a check query:

SELECT 
DB_NAME(database_id) AS [Database Name], 
COUNT(*) AS [Page Count], 
COUNT(*) * 8 / 1024 AS [Memory Usage (MB)]
FROM 
sys.dm_os_buffer_descriptors
WHERE 
database_id = DB_ID('ENEXRHO')
GROUP BY 
database_id;