SQL SERVER占用CPU过高排查和优化

SQL优化方法：

　　1、查看连接对象

 USE master
 GO
 --如果要指定数据库就把注释去掉
 SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])='gposdb'

2、然后使用下面语句看一下各项指标是否正常，是否有阻塞，正常情况下搜索结果应该为空。

SELECT TOP 10
[session_id],
[request_id],
[start_time] AS '开始时间',
[status] AS '状态',
[command] AS '命令',
dest.[text] AS 'sql语句',
DB_NAME([database_id]) AS '数据库名',
[blocking_session_id] AS '正在阻塞其他会话的会话ID',
[wait_type] AS '等待资源类型',
[wait_time] AS '等待时间',
[wait_resource] AS '等待的资源',
[reads] AS '物理读次数',
[writes] AS '写次数',
[logical_reads] AS '逻辑读次数',
[row_count] AS '返回结果行数'
FROM sys.[dm_exec_requests] AS der
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50 AND DB_NAME(der.[database_id])='gposdb'
ORDER BY [cpu_time] DESC

3.查看是哪些SQL语句占用较大可以使用下面代码

--在SSMS里选择以文本格式显示结果
SELECT TOP 10
dest.[text] AS 'sql语句'
FROM sys.[dm_exec_requests] AS der
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50
ORDER BY [cpu_time] DESC

3、如果SQLSERVER存在要等待的资源，那么执行下面语句就会显示出会话中有多少个worker在等待

SELECT TOP 10
[session_id],
[request_id],
[start_time] AS '开始时间',
[status] AS '状态',
[command] AS '命令',
dest.[text] AS 'sql语句',
DB_NAME([database_id]) AS '数据库名',
[blocking_session_id] AS '正在阻塞其他会话的会话ID',
der.[wait_type] AS '等待资源类型',
[wait_time] AS '等待时间',
[wait_resource] AS '等待的资源',
[dows].[waiting_tasks_count] AS '当前正在进行等待的任务数',
[reads] AS '物理读次数',
[writes] AS '写次数',
[logical_reads] AS '逻辑读次数',
[row_count] AS '返回结果行数'
FROM sys.[dm_exec_requests] AS der
INNER JOIN [sys].[dm_os_wait_stats] AS dows
ON der.[wait_type]=[dows].[wait_type]
CROSS APPLY
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
WHERE [session_id]>50
ORDER BY [cpu_time] DESC

4.查询CPU占用最高的SQL语句

SELECT TOP 10
total_worker_time/execution_count AS avg_cpu_cost, plan_handle,
execution_count,
(SELECT SUBSTRING(text, statement_start_offset/2 + 1,
(CASE WHEN statement_end_offset = -1
THEN LEN(CONVERT(nvarchar(max), text)) * 2
ELSE statement_end_offset
END - statement_start_offset)/2)
FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
FROM sys.dm_exec_query_stats
ORDER BY [avg_cpu_cost] DESC

5、索引缺失查询

SELECT
DatabaseName = DB_NAME(database_id)
,[Number Indexes Missing] = count(*)
FROM sys.dm_db_missing_index_details
GROUP BY DB_NAME(database_id)
ORDER BY 2 DESC;
SELECT TOP 10
[Total Cost] = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0)
, avg_user_impact
, TableName = statement
, [EqualityUsage] = equality_columns
, [InequalityUsage] = inequality_columns
, [Include Cloumns] = included_columns
FROM sys.dm_db_missing_index_groups g
INNER JOIN sys.dm_db_missing_index_group_stats s
ON s.group_handle = g.index_group_handle
INNER JOIN sys.dm_db_missing_index_details d
ON d.index_handle = g.index_handle
ORDER BY [Total Cost] DESC;