SQL优化方法：

1、查看连接对象

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

　　

　　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。

 1 SELECT TOP 10
 2 [session_id],
 3 [request_id],
 4 [start_time] AS '开始时间',
 5 [status] AS '状态',
 6 [command] AS '命令',
 7 dest.[text] AS 'sql语句',
 8 DB_NAME([database_id]) AS '数据库名',
 9 [blocking_session_id] AS '正在阻塞其他会话的会话ID',
10 [wait_type] AS '等待资源类型',
11 [wait_time] AS '等待时间',
12 [wait_resource] AS '等待的资源',
13 [reads] AS '物理读次数',
14 [writes] AS '写次数',
15 [logical_reads] AS '逻辑读次数',
16 [row_count] AS '返回结果行数'
17 FROM sys.[dm_exec_requests] AS der
18 CROSS APPLY
19 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
20 WHERE [session_id]>50 AND DB_NAME(der.[database_id])='gposdb'
21 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

1 --在SSMS里选择以文本格式显示结果
2 SELECT TOP 10
3 dest.[text] AS 'sql语句'
4 FROM sys.[dm_exec_requests] AS der
5 CROSS APPLY
6 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
7 WHERE [session_id]>50
8 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

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

4、查询CPU占用最高的SQL语句

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

5、索引缺失查询

 1 SELECT
 2     DatabaseName = DB_NAME(database_id)
 3     ,[Number Indexes Missing] = count(*)
 4 FROM sys.dm_db_missing_index_details
 5 GROUP BY DB_NAME(database_id)
 6 ORDER BY 2 DESC;
 7 SELECT  TOP 10
 8         [Total Cost]  = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0)
 9         , avg_user_impact
10         , TableName = statement
11         , [EqualityUsage] = equality_columns
12         , [InequalityUsage] = inequality_columns
13         , [Include Cloumns] = included_columns
14 FROM        sys.dm_db_missing_index_groups g
15 INNER JOIN    sys.dm_db_missing_index_group_stats s
16        ON s.group_handle = g.index_group_handle
17 INNER JOIN    sys.dm_db_missing_index_details d
18        ON d.index_handle = g.index_handle
19 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。