一、破坏死锁的四个必要条件

二、如果发生死锁，通过SQL语句关闭当前发生死锁的数据库进程

USE master --不能用 KILL 来取消您自己的进程。

GO
/****** Object:  StoredProcedure [dbo].[p_Centaline_Who_Lock]    Script Date: 03/23/2016 11:54:38 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[p_killspid]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
drop procedure [dbo].[p_killspid]
GO

create proc p_killspid
@dbname varchar(200)    --要关闭进程的数据库名
as 
    declare @sql  nvarchar(500) 
    declare @spid nvarchar(20)

declare #tb cursor for
        select spid=cast(spid as varchar(20)) from master..sysprocesses where dbid=db_id(@dbname)
    open #tb
    fetch next from #tb into @spid
    while @@fetch_status=0
    begin 
        exec('kill '+@spid)
        fetch next from #tb into @spid
    end 
    close #tb
    deallocate #tb
go

调用

exec p_killspid  '需要关闭进程的数据库名'  当强制关闭进程后，死锁也就没有了

二、查看当前数据库下锁的情况

CREATE Table #Who(

spid int,

ecid int,

[status] nvarchar(50),

loginname nvarchar(50),

hostname nvarchar(50),

blk int,

dbname nvarchar(50),

cmd nvarchar(50)

--request_ID int

);

CREATE Table #Lock(

spid int,

dpid int,

[objid] int,

indld int,

[Type] nvarchar(20),

[Resource] nvarchar(50),

Mode nvarchar(10),

[Status] nvarchar(10)

);

INSERT INTO #Who

EXEC sp_who active  --看哪个引起的阻塞，blk

INSERT INTO #Lock

EXEC sp_lock  --看锁住了那个资源id，objid

DECLARE @DBName nvarchar(20);

SET @DBName='KF-BJAgencyAtt'

SELECT #Who.* FROM #Who WHERE dbname=@DBName

SELECT #Lock.* FROM #Lock

JOIN #Who

ON #Who.spid=#Lock.spid

AND dbname=@DBName;

--最后发送到SQL Server的语句

DECLARE crsr Cursor FOR

SELECT blk FROM #Who WHERE dbname=@DBName AND blk<>0;

DECLARE @blk int;

open crsr;

FETCH NEXT FROM crsr INTO @blk;

WHILE (@@FETCH_STATUS = 0)

BEGIN

dbcc inputbuffer(@blk);

FETCH NEXT FROM crsr INTO @blk;

END

close crsr;

DEALLOCATE crsr;

--锁定的资源

SELECT #Who.spid,hostname,objid,[type],mode,object_name(objid) as objName FROM #Lock

JOIN #Who

ON #Who.spid=#Lock.spid

AND dbname=@DBName

WHERE objid<>0;

--SELECT * FROM   #Lock

DROP Table #Who;

DROP Table #Lock;

查看死锁实例

BEGIN tran
        UPDATE B SET age=age+1
        WaitFor Delay '00:00:05';
        SELECT * FROM A     --执行完之后有结果

在新建一个查询，执行下面sql语句

BEGIN tran
          UPDATE a SET dd=dd+1

WaitFor Delay '00:00:05';
          SELECT * FROM B

ROLLBACK tran   --当执行的时候会一直执行下去

查看出现死锁语句