查 TOP CPU/IO/时间长的，看看历史上那些是影响大的，可以用这个

WITH

DATA AS(

SELECT * FROM sys.dm_exec_query_stats WITH(NOLOCK)

WHERE last_execution_time >= DATEDIFF(DAY, 7, GETDATE())

AND execution_count >= 7

)

SELECT QS.*, ST.*, QP.query_plan

FROM(

SELECT TOP 10 __$type = 'CPU', * FROM DATA

WHERE total_worker_time > 0

ORDER BY CONVERT(float, total_worker_time)/execution_count DESC

UNION ALL

SELECT TOP 10 __$type = 'IO', * FROM DATA

WHERE total_logical_reads+total_logical_writes > 0

ORDER BY CONVERT(float, total_logical_reads+total_logical_writes)/execution_count DESC

UNION ALL

SELECT TOP 10 __$type = 'Duration', * FROM DATA

WHERE total_elapsed_time > 0

ORDER BY CONVERT(float, total_elapsed_time)/execution_count DESC

) QS

CROSS APPLY sys.dm_exec_sql_text(QS.sql_handle) ST

OUTER APPLY sys.dm_exec_query_plan(QS.plan_handle) As QP

查到问题语句，再根据相关语句的执行计划进行优化调整。