SQL SERVER占用CPU过高优化

　　操作系统是Windows2008R2 ,数据库是SQL2014 64位。

　　近阶段服务器出现过几次死机，管理员反馈机器内存使用率100%导致机器卡死。于是做了个监测服务器的软件实时记录CPU数据，几日观察得出数据如下：

　　SQL优化方法：

　　1、查看连接对象

SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])=\'gposdb\'

select client_net_address \'客户端IP\',local_net_address \'服务器的IP\',* from sys.dm_exec_connections

　　当前连接对象有67个其中‘WINAME’的主机名，‘jTDS’的进程名不属于已知常用软件，找到这台主机并解决连接问题。在360流量防火墙中查看有哪个软件连接了服务器IP，除之。

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

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;

　找到索引缺失的表，根据查询结果中的关键次逐一建立索引。

　　做完这些测试，基本能找到问题。