Find memory in use by sql databases

Run this query in SSMS to show how much memory the DB’s are currently using.

DECLARE @total_buffer INT;

SELECT @total_buffer = cntr_value
FROM sys.dm_os_performance_counters 
WHERE RTRIM([object_name]) LIKE '%Buffer Manager'
AND counter_name = 'Database Pages';

;WITH src AS
(
SELECT 
database_id, db_buffer_pages = COUNT_BIG(*)
FROM sys.dm_os_buffer_descriptors
--WHERE database_id BETWEEN 5 AND 32766
GROUP BY database_id
)
SELECT
[db_name] = CASE [database_id] WHEN 32767 
THEN 'Resource DB' 
ELSE DB_NAME([database_id]) END,
db_buffer_pages,
db_buffer_MB = db_buffer_pages / 128,
db_buffer_percent = CONVERT(DECIMAL(6,3), 
db_buffer_pages * 100.0 / @total_buffer)
FROM src
ORDER BY db_buffer_MB DESC;