MSSQ调优所需用的语句

看一下各项指标是否正常，是否有阻塞，这个语句选取了前10个最耗CPU时间的会话语句

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

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，如果没有则下面语句运行结果为空。

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',
 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

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

查询缺失索引

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;

使用DMV来分析SQL Server启动以来累计使用CPU资源最多的语句。例如下面的语句就可以列出前50名

select 
    c.last_execution_time,c.execution_count,c.total_logical_reads,c.total_logical_writes,c.total_elapsed_time,c.last_elapsed_time, 
    q.[text]
from 
    (select top 50 qs.*
    from sys.dm_exec_query_stats qs
    order by qs.total_worker_time desc) as c
    cross apply sys.dm_exec_sql_text(plan_handle) as q
order by c.total_worker_time desc
go

返回最经常运行的100条语句

SELECT TOP 100 cp.cacheobjtype,cp.usecounts,cp.size_in_bytes,qs.statement_start_offset,qs.statement_end_offset,qt.dbid    ,qt.objectid
                        ,SUBSTRING(qt.text,qs.statement_start_offset/2, 
                        (case when qs.statement_end_offset = -1 
                        then len(convert(nvarchar(max), qt.text)) * 2 
                        else qs.statement_end_offset end -qs.statement_start_offset)/2)     as statement 
FROM sys.dm_exec_query_stats qs
cross apply sys.dm_exec_sql_text(qs.sql_handle) as qt
inner join sys.dm_exec_cached_plans as cp on qs.plan_handle=cp.plan_handle
where cp.plan_handle=qs.plan_handle
and cp.usecounts>4
ORDER BY [dbid],[Usecounts] DESC

返回做IO数目最多的50条语句以及它们的执行计划

SELECT TOP 100 cp.cacheobjtype,cp.usecounts,cp.size_in_bytes,qs.statement_start_offset,qs.statement_end_offset,qt.dbid    ,qt.objectid
                        ,SUBSTRING(qt.text,qs.statement_start_offset/2, 
                        (case when qs.statement_end_offset = -1 
                        then len(convert(nvarchar(max), qt.text)) * 2 
                        else qs.statement_end_offset end -qs.statement_start_offset)/2)     as statement 
FROM sys.dm_exec_query_stats qs
cross apply sys.dm_exec_sql_text(qs.sql_handle) as qt
inner join sys.dm_exec_cached_plans as cp on qs.plan_handle=cp.plan_handle
where cp.plan_handle=qs.plan_handle
and cp.usecounts>4
select top 50 
    (total_logical_reads/execution_count) as avg_logical_reads,
    (total_logical_writes/execution_count) as avg_logical_writes,
    (total_physical_reads/execution_count) as avg_phys_reads,
     Execution_count, 
    statement_start_offset as stmt_start_offset, statement_end_offset as stmt_end_offset,
substring(sql_text.text, (statement_start_offset/2), 
case 
when (statement_end_offset -statement_start_offset)/2 <=0 then 64000
else (statement_end_offset -statement_start_offset)/2 end) as exec_statement,  sql_text.text,plan_text.*
from sys.dm_exec_query_stats  
cross apply sys.dm_exec_sql_text(sql_handle) as sql_text
cross apply sys.dm_exec_query_plan(plan_handle) as plan_text
order by 
 (total_logical_reads + total_logical_writes) /Execution_count Desc

计算signal wait占整wait时间的百分比
指令等待 CPU 资源的时间占总时间的百分比。如果超过 25% ，说明 CPU 紧张

select convert(numeric(5,4),sum(signal_wait_time_ms)/sum(wait_time_ms)) 
from Sys.dm_os_wait_stats 

-- 计算'Cxpacket'占整wait时间的百分比
-- Cxpacket:Sql Server 在处理一句代价很大的语句，要不就是没有合适的索引或筛选条件没能筛选足够的记录，使得语句要返回大量的结果，当 >5% 说明有问题
declare @Cxpacket bigint
declare @Sumwaits bigint
select @Cxpacket = wait_time_ms
from Sys.dm_os_wait_stats
where wait_type = 'Cxpacket'
select @Sumwaits = sum(wait_time_ms)
from Sys.dm_os_wait_stats
select convert(numeric(5,4),@Cxpacket/@Sumwaits)

查询当前数据库上所有用户表格在Row lock上发生阻塞的频率

declare @dbid int
select @dbid = db_id()
Select dbid=database_id, objectname=object_name(s.object_id)
, indexname=i.name, i.index_id    --, partition_number
, row_lock_count, row_lock_wait_count
, [block %]=cast (100.0 * row_lock_wait_count / (1 + row_lock_count) as numeric(15,2))
, row_lock_wait_in_ms
, [avg row lock waits in ms]=cast (1.0 * row_lock_wait_in_ms / (1 + row_lock_wait_count) as numeric(15,2))
from sys.dm_db_index_operational_stats (@dbid, NULL, NULL, NULL) s,     sys.indexes i
where objectproperty(s.object_id,'IsUserTable') = 1
and i.object_id = s.object_id
and i.index_id = s.index_id
order by row_lock_wait_count desc

--Begin Index(索引) 分析优化的相关 Sql 

-- 返回当前数据库所有碎片率大于25%的索引
-- 运行本语句会扫描很多数据页面
-- 避免在系统负载比较高时运行
-- 避免在系统负载比较高时运行
declare @dbid int
select @dbid = db_id()
SELECT o.name as tablename,s.* FROM sys.dm_db_index_physical_stats (@dbid, NULL, NULL, NULL, NULL) s,sys.objects o
where avg_fragmentation_in_percent>25 and o.object_id =s.object_id
order by avg_fragmentation_in_percent desc
GO

-- 当前数据库可能缺少的索引
-- 非常好用的 Sql 语句
select d.*
        , s.avg_total_user_cost
        , s.avg_user_impact
        , s.last_user_seek
        ,s.unique_compiles
from sys.dm_db_missing_index_group_stats s
        ,sys.dm_db_missing_index_groups g
        ,sys.dm_db_missing_index_details d
where s.group_handle = g.index_group_handle
and d.index_handle = g.index_handle
order by s.avg_user_impact desc
go

-- 自动重建或重新组织索引
-- 比较好用，慎用，特别是对于在线 DB
-- Ensure a USE <databasename> statement has been executed first.
SET NOCOUNT ON;
DECLARE @objectid int;
DECLARE @indexid int;
DECLARE @partitioncount bigint;
DECLARE @schemaname nvarchar(130); 
DECLARE @objectname nvarchar(130); 
DECLARE @indexname nvarchar(130); 
DECLARE @partitionnum bigint;
DECLARE @partitions bigint;
DECLARE @frag float;
DECLARE @command nvarchar(4000); 
-- Conditionally select tables and indexes from the sys.dm_db_index_physical_stats function 
-- and convert object and index IDs to names.
SELECT
    object_id AS objectid,
    index_id AS indexid,
    partition_number AS partitionnum,
    avg_fragmentation_in_percent AS frag
INTO #work_to_do
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL , NULL, 'LIMITED')
WHERE avg_fragmentation_in_percent > 10.0 AND index_id > 0;

-- Declare the cursor for the list of partitions to be processed.
DECLARE partitions CURSOR FOR SELECT * FROM #work_to_do;

-- Open the cursor.
OPEN partitions;

-- Loop through the partitions.
WHILE (1=1)
    BEGIN;
        FETCH NEXT
           FROM partitions
           INTO @objectid, @indexid, @partitionnum, @frag;
        IF @@FETCH_STATUS < 0 BREAK;
        SELECT @objectname = QUOTENAME(o.name), @schemaname = QUOTENAME(s.name)
        FROM sys.objects AS o
        JOIN sys.schemas as s ON s.schema_id = o.schema_id
        WHERE o.object_id = @objectid;
        SELECT @indexname = QUOTENAME(name)
        FROM sys.indexes
        WHERE  object_id = @objectid AND index_id = @indexid;
        SELECT @partitioncount = count (*)
        FROM sys.partitions
        WHERE object_id = @objectid AND index_id = @indexid;

-- 30 is an arbitrary decision point at which to switch between reorganizing and rebuilding.
        IF @frag < 30.0
            SET @command = N'ALTER INDEX ' + @indexname + N' ON ' + @schemaname + N'.' + @objectname + N' REORGANIZE';
        IF @frag >= 30.0
            SET @command = N'ALTER INDEX ' + @indexname + N' ON ' + @schemaname + N'.' + @objectname + N' REBUILD';
        IF @partitioncount > 1
            SET @command = @command + N' PARTITION=' + CAST(@partitionnum AS nvarchar(10));
        EXEC (@command);
        PRINT N'Executed: ' + @command;
    END;

-- Close and deallocate the cursor.
CLOSE partitions;
DEALLOCATE partitions;

-- Drop the temporary table.
DROP TABLE #work_to_do;
GO


-- 查看当前数据库索引的使用率
-- 非常的有用
SELECT
object_name(object_id) as table_name,
(
select name
from sys.indexes
where object_id = stats.object_id and index_id = stats.index_id
) as index_name,
*
FROM sys.dm_db_index_usage_stats as stats
WHERE database_id = DB_ID()
order by table_name


-- 指定表的索引使用情况
declare @table as nvarchar(100)
set @table = 't_name';

SELECT
(
  select name
  from sys.indexes
  where object_id = stats.object_id and index_id = stats.index_id
) as index_name,
*
FROM sys.dm_db_index_usage_stats as stats
where object_id = object_id(@table)
order by user_seeks, user_scans, user_lookups asc

--End Index 分析优化的相关 Sql