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[数据库]SQL语句导致cpu占用如此高


一般我们可以使用sql server自带的性能分析追踪工具sql profiler分析数据库设计所产生问题的来源,进行有针对性的处理。但我们也可以通过自己写SQL语句来有针对性的进行性能方面的查询。通常会用到如下三个系统视图:sys.sysprocesses ,dm_exec_sessions ,dm_exec_requests

--一、查看当前的数据库用户连接有多少
USE master

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

SELECT COUNT(*)
FROM [sys].[dm_exec_sessions]
WHERE [session_id] > 50

--二、选取前10个最耗CPU时间的会话
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

--三、查询前10个最耗CPU时间的SQL语句
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

--四、查询会话中有多少个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

--五、查询CPU占用高的语句
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