SQL語句導致cpu占用如此高

一般我們可以使用sql server自帶的性能分析追蹤工具sql profiler分析資料庫設計所產生問題的來源，進行有針對性的處理。但我們也可以通過自己寫SQL語句來有針對性的進行性能方面的查詢。通常會用到如下三個系統視圖：sys.sysprocesses ,dm_exec_sessions ,dm_exec_requests

--一、查看當前的資料庫用戶連接有多少
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、選取前10個最耗CPU時間的會話
SELECT TOP 10
[session_id] ,
[request_id] ,
[start_time] AS '開始時間' ,
[status] AS '狀態' ,
[command] AS '命令' ,
dest.[text] AS 'sql語句' ,
DB_NAME([database_id]) AS '資料庫名' ,
[blocking_session_id] AS '正在阻塞其他會話的會話ID' ,
[wait_type] AS '等待資源類型' ,
[wait_time] AS '等待時間' ,
[wait_resource] AS '等待的資源' ,
[reads] AS '物理讀次數' ,
[writes] AS '寫次數' ,
[logical_reads] AS '邏輯讀次數' ,
[row_count] AS '返回結果行數'
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、查詢前10個最耗CPU時間的SQL語句
SELECT TOP 10
dest.[text] AS 'sql語句'
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、查詢會話中有多少個worker在等待 
SELECT TOP 10
[session_id] ,
[request_id] ,
[start_time] AS '開始時間' ,
[status] AS '狀態' ,
[command] AS '命令' ,
dest.[text] AS 'sql語句' ,
DB_NAME([database_id]) AS '資料庫名' ,
[blocking_session_id] AS '正在阻塞其他會話的會話ID' ,
der.[wait_type] AS '等待資源類型' ,
[wait_time] AS '等待時間' ,
[wait_resource] AS '等待的資源' ,
[dows].[waiting_tasks_count] AS '當前正在進行等待的任務數' ,
[reads] AS '物理讀次數' ,
[writes] AS '寫次數' ,
[logical_reads] AS '邏輯讀次數' ,
[row_count] AS '返回結果行數'
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、查詢CPU占用高的語句
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