索引的重要性

       发现一个操作事务经常死锁，特别是客户端操作人数多的话，后面根据LOG发现执行时间长达数百毫秒。所以需要优化数据库分析

 

首先要勾选开启执行计划

然后输入对应的语句，然后执行，下面就有具体的查询计划，哪些占用了时间

语句类似这样insert into test(name)  select 'aa' where not exists(seelct 1 from test where name = 'aa')

这个语句是会去扫描表test的，如果数据量大，比如test表包含了100万条记录，就非常有必要在test表对name 增加一个索引

非常有效果。

附加查看死锁脚本

create procedure [dbo].[sp_who_lock]
as
begin
declare @spid int,@bl int,
 @intTransactionCountOnEntry  int,
        @intRowcount    int,
        @intCountProperties   int,
        @intCounter    int

 create table #tmp_lock_who (
 id int identity(1,1),
 spid smallint,
 bl smallint)
 
 IF @@ERROR<>0 RETURN @@ERROR
 
 insert into #tmp_lock_who(spid,bl) select  0 ,blocked
   from (select * from sysprocesses where  blocked>0 ) a 
   where not exists(select * from (select * from sysprocesses where  blocked>0 ) b 
   where a.blocked=spid)
   union select spid,blocked from sysprocesses where  blocked>0

 IF @@ERROR<>0 RETURN @@ERROR 
  
-- 找到临时表的记录数
 select  @intCountProperties = Count(*),@intCounter = 1
 from #tmp_lock_who
 
 IF @@ERROR<>0 RETURN @@ERROR 
 
 if @intCountProperties=0
  select '现在没有阻塞和死锁信息' as message

-- 循环开始
while @intCounter <= @intCountProperties
begin
-- 取第一条记录
  select  @spid = spid,@bl = bl
  from #tmp_lock_who where Id = @intCounter 
 begin
  if @spid =0 
            select '引起数据库死锁的是: '+ CAST(@bl AS VARCHAR(10)) + '进程号,其执行的SQL语法如下'
 else
            select '进程号SPID：'+ CAST(@spid AS VARCHAR(10))+ '被' + '进程号SPID：'+ CAST(@bl AS VARCHAR(10)) +'阻塞,其当前进程执行的SQL语法如下'
 DBCC INPUTBUFFER (@bl )
 end 

-- 循环指针下移
 set @intCounter = @intCounter + 1
end

drop table #tmp_lock_who

return 0
end

 

附加查看语句执行时间：毫秒数

declare @ct datetime
set @ct = getdate()

select * from test

select datediff(ms,@ct,getdate()) as 'time'