sqlserver 缓存命中率查询

SELECT (a.cntr_value * 1.0 / b.cntr_value) * 100.0 [BufferCacheHitRatio]
FROM (SELECT * FROM sys.dm_os_performance_counters
WHERE counter_name = 'Buffer cache hit ratio'
AND object_name = CASE WHEN @@SERVICENAME = 'MSSQLSERVER'
THEN 'SQLServer:Buffer Manager'
ELSE 'MSSQL$' + rtrim(@@SERVICENAME) +
':Buffer Manager' END ) a
CROSS JOIN
(SELECT * from sys.dm_os_performance_counters
WHERE counter_name = 'Buffer cache hit ratio base'
and object_name = CASE WHEN @@SERVICENAME = 'MSSQLSERVER'
THEN 'SQLServer:Buffer Manager'
ELSE 'MSSQL$' + rtrim(@@SERVICENAME) +
':Buffer Manager' END ) b;