SQL Server优化常用SQL语句

--所有没有主键的表
select name from sysobjects where xtype='U' and id not in
(
select i.parent_obj from sysobjects i
where i.xtype='PK' 
) order by name

--逻辑读最多的语句
SELECT TOP 10
        (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
       ,(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
       --,plan_handle
       ,db_name(qp.dbid)
       ,qp.query_plan
FROM    sys.dm_exec_query_stats
cross apply sys.dm_exec_query_plan(plan_handle) qp
ORDER BY (total_logical_reads + total_logical_writes)/execution_count DESC

--未被使用过的索引
SELECT  o.name Object_Name     --表名
      , i.name Index_name     --索引名
      , i.Type_Desc             --是否聚集索引
      , s.user_seeks         --索引seek的次数
      , s.user_scans         --索引scan的次数
      , s.user_updates         --索引update的次数
      , s.user_lookups         --索引lookup的次数
FROM    sys.objects AS o
JOIN    sys.indexes AS i
ON      o.object_id = i.object_id
LEFT OUTER   JOIN sys.dm_db_index_usage_stats AS s
ON      i.object_id = s.object_id
        AND i.index_id = s.index_id
WHERE   o.type = 'u' 
and i.type_desc <> 'heap'
and user_seeks=0 
and user_scans=0
ORDER BY OBJECT_NAME;

--总耗CPU最多的前个SQL:
SELECT TOP 50
    total_worker_time/1000 AS [总消耗CPU 时间(ms)],execution_count [运行次数],
    qs.total_worker_time/qs.execution_count/1000 AS [平均消耗CPU 时间(ms)],
    min_worker_time /1000 AS [最小执行时间(ms)],
    max_worker_time /1000 AS [最大执行时间(ms)],last_execution_time AS [最后一次执行时间],
    SUBSTRING(qt.text,qs.statement_start_offset/2+1, 
        (CASE WHEN qs.statement_end_offset = -1 
        THEN DATALENGTH(qt.text) 
        ELSE qs.statement_end_offset END -qs.statement_start_offset)/2 + 1) 
    AS [使用CPU的语法],
    dbname=db_name(qt.dbid),
    object_name(qt.objectid,qt.dbid) ObjectName
FROM sys.dm_exec_query_stats qs WITH(nolock)
CROSS apply sys.dm_exec_sql_text(qs.sql_handle) AS qt
WHERE execution_count>1  
and (db_name(qt.dbid)='xxxx' or db_name(qt.dbid) is null)
--and (qs.total_worker_time/qs.execution_count/1000)>300
and last_execution_time>'2015-05-12'
ORDER BY  
total_worker_time desc
,(qs.total_worker_time/qs.execution_count/1000) desc

--查询用户表的索引
SELECT   
 c.name as 表名  
,a.name as 索引名称
,d.name as 索引字段名 
,d.colid as 索引字段位置 
,case d.xusertype when 104 then '索引键列' else '包含性列' end 列类型
FROM   sysindexes   a  
JOIN   sysindexkeys   b   ON   a.id=b.id   AND   a.indid=b.indid  
JOIN   sysobjects   c   ON   b.id=c.id  
JOIN   syscolumns   d   ON   b.id=d.id   AND   b.colid=d.colid  
WHERE   a.indid   NOT IN(0,255) and   c.xtype='U'
AND   c.name='BillDetail' --查指定表  
ORDER BY   c.name,a.name

--当前库所有表的记录数
select   a.name as 表名,max(b.rows) as 记录条数   from   sysobjects   a   ,sysindexes   b     
  where   a.id=b.id   and   a.xtype='u'   
group   by   a.name   
order by max(b.rows) desc