首先说一下一个sql server 没有公开的存储过程:sp_msforeach_worker

以下是生成该存储过程的SQL语句:

/*******************************************************
sp_MSforeach_worker 系统存储过程共4个参数
      @command1    nvarchar(2000) --第一条运行的t-sql指令
      @replacechar    nchar(1)            --指定的占位符号
      @command2    nvarchar(2000) --第二条运行的t-sql指令
      @command3    nvarchar(2000)  --第三条运行的t-sql指令
********************************************************/
/*  
* This is the worker proc for all of the "for each" type procs.  Its function is to read the  
* next replacement name from the cursor (which returns only a single name), plug it into the  
* replacement locations for the commands, and execute them.  It assumes the cursor "hCForEach"  
* has already been opened by its caller.  
*/  
create proc sp_MSforeach_worker  
@command1 nvarchar(2000), @replacechar nchar(1) = N'?', @command2 nvarchar(2000) = null, @command3 nvarchar(2000) = null  
as  
  
create table #qtemp ( /* Temp command storage */  
  qnum    int    NOT NULL,  
  qchar    nvarchar(2000) COLLATE database_default NULL  
)  
  
set nocount on  
declare @name nvarchar(517), @namelen int, @q1 nvarchar(2000), @q2 nvarchar(2000)  
   declare @q3 nvarchar(2000), @q4 nvarchar(2000), @q5 nvarchar(2000)  
declare @q6 nvarchar(2000), @q7 nvarchar(2000), @q8 nvarchar(2000), @q9 nvarchar(2000), @q10 nvarchar(2000)  
declare @cmd nvarchar(2000), @replacecharindex int, @useq tinyint, @usecmd tinyint, @nextcmd nvarchar(2000)  
   declare @namesave nvarchar(517), @nametmp nvarchar(517), @nametmp2 nvarchar(258)  
  
open hCForEach
fetch hCForEach into @name  
  
/* Loop for each database */  
while (@@fetch_status >= 0) begin  
  /* Initialize. */  
  
      /* save the original dbname */  
      select @namesave = @name  
  select @useq = 1, @usecmd = 1, @cmd = @command1, @namelen = datalength(@name)  
  while (@cmd is not null) begin  /* Generate @q* for exec() */  
   /*  
    * Parse each @commandX into a single executable batch.  
    * Because the expanded form of a @commandX may be > OSQL_MAXCOLLEN_SET, we'll need to allow overflow.  
    * We also may append @commandX's (signified by '++' as first letters of next @command).  
    */  
   select @replacecharindex = charindex(@replacechar, @cmd)  
   while (@replacecharindex <> 0) begin  
  
            /* 7.0, if name contains ' character, and the name has been single quoted in command, double all of them in dbname */  
            /* if the name has not been single quoted in command, do not doulbe them */  
            /* if name contains ] character, and the name has been [] quoted in command, double all of ] in dbname */  
            select @name = @namesave  
            select @namelen = datalength(@name)  
            declare @tempindex int  
            if (substring(@cmd, @replacecharindex - 1, 1) = N'''') begin  
               /* if ? Is inside of '', we need to double all the ' in name */  
               select @name = REPLACE(@name, N'''', N'''''')  
            end else if (substring(@cmd, @replacecharindex - 1, 1) = N'[') begin  
               /* if ? Is inside of [], we need to double all the ] in name */  
               select @name = REPLACE(@name, N']', N']]')  
            end else if ((@name LIKE N'%].%]') and (substring(@name, 1, 1) = N'[')) begin  
               /* ? Is NOT inside of [] nor '', and the name is in [owner].[name] format, handle it */  
               /* !!! Work around, when using LIKE to find string pattern, can't use '[', since LIKE operator is treating '[' as a wide char */  
               select @tempindex = charindex(N'].[', @name)  
               select @nametmp  = substring(@name, 2, @tempindex-2 )  
               select @nametmp2 = substring(@name, @tempindex+3, len(@name)-@tempindex-3 )  
               select @nametmp  = REPLACE(@nametmp, N']', N']]')  
               select @nametmp2 = REPLACE(@nametmp2, N']', N']]')  
               select @name = N'[' + @nametmp + N'].[' + @nametmp2 + ']'  
            end else if ((@name LIKE N'%]') and (substring(@name, 1, 1) = N'[')) begin  
               /* ? Is NOT inside of [] nor '', and the name is in [name] format, handle it */  
               /* j.i.c., since we should not fall into this case */  
               /* !!! Work around, when using LIKE to find string pattern, can't use '[', since LIKE operator is treating '[' as a wide char */  
               select @nametmp = substring(@name, 2, len(@name)-2 )  
         select @nametmp = REPLACE(@nametmp, N']', N']]')  
               select @name = N'[' + @nametmp + N']'  
            end  
            /* Get the new length */  
            select @namelen = datalength(@name)  
  
            /* start normal process */  
    if (datalength(@cmd) + @namelen - 1 > 2000) begin  
     /* Overflow; put preceding stuff into the temp table */  
     if (@useq > 9) begin  
      raiserror 55555 N'sp_Msforeach_worker assert failed:  command too long'  
      close hCForEach  
      deallocate hCForEach  
      return 1  
     end  
     if (@replacecharindex < @namelen) begin  
      /* If this happened close to beginning, make sure expansion has enough room. */  
      /* In this case no trailing space can occur as the row ends with @name. */  
      select @nextcmd = substring(@cmd, 1, @replacecharindex)  
      select @cmd = substring(@cmd, @replacecharindex + 1, 2000)  
      select @nextcmd = stuff(@nextcmd, @replacecharindex, 1, @name)  
      select @replacecharindex = charindex(@replacechar, @cmd)  
      insert #qtemp values (@useq, @nextcmd)  
      select @useq = @useq + 1  
      continue  
     end  
     /* Move the string down and stuff() in-place. */  
     /* Because varchar columns trim trailing spaces, we may need to prepend one to the following string. */  
     /* In this case, the char to be replaced is moved over by one. */  
     insert #qtemp values (@useq, substring(@cmd, 1, @replacecharindex - 1))  
     if (substring(@cmd, @replacecharindex - 1, 1) = N' ') begin  
      select @cmd = N' ' + substring(@cmd, @replacecharindex, 2000)  
      select @replacecharindex = 2  
     end else begin  
      select @cmd = substring(@cmd, @replacecharindex, 2000)  
      select @replacecharindex = 1  
     end  
     select @useq = @useq + 1  
    end  
    select @cmd = stuff(@cmd, @replacecharindex, 1, @name)  
    select @replacecharindex = charindex(@replacechar, @cmd)  
   end  
  
   /* Done replacing for current @cmd.  Get the next one and see if it's to be appended. */  
   select @usecmd = @usecmd + 1  
   select @nextcmd = case (@usecmd) when 2 then @command2 when 3 then @command3 else null end  
   if (@nextcmd is not null and substring(@nextcmd, 1, 2) = N'++') begin  
    insert #qtemp values (@useq, @cmd)  
    select @cmd = substring(@nextcmd, 3, 2000), @useq = @useq + 1  
    continue  
   end  
  
   /* Now exec() the generated @q*, and see if we had more commands to exec().  Continue even if errors. */  
   /* Null them first as the no-result-set case won't. */  
   select @q1 = null, @q2 = null, @q3 = null, @q4 = null, @q5 = null, @q6 = null, @q7 = null, @q8 = null, @q9 = null, @q10 = null  
   select @q1 = qchar from #qtemp where qnum = 1  
   select @q2 = qchar from #qtemp where qnum = 2  
   select @q3 = qchar from #qtemp where qnum = 3  
   select @q4 = qchar from #qtemp where qnum = 4  
   select @q5 = qchar from #qtemp where qnum = 5  
   select @q6 = qchar from #qtemp where qnum = 6  
   select @q7 = qchar from #qtemp where qnum = 7  
   select @q8 = qchar from #qtemp where qnum = 8  
   select @q9 = qchar from #qtemp where qnum = 9  
   select @q10 = qchar from #qtemp where qnum = 10  
   truncate table #qtemp  
   exec (@q1 + @q2 + @q3 + @q4 + @q5 + @q6 + @q7 + @q8 + @q9 + @q10 + @cmd)  
   select @cmd = @nextcmd, @useq = 1  
  end /* while @cmd is not null, generating @q* for exec() */  
  
  /* All commands done for this name.  Go to next one. */  
  fetch hCForEach into @name  
end /* while FETCH_SUCCESS */  
close hCForEach  
deallocate hCForEach  
return 0

备注：使用此过程前必须手工声明一名为 hCForEach 的全局游标

<隐藏代码可以不看>

exec(N'declare hCForEach cursor global for select name from master.dbo.sysdatabases d ' +  
   N' where (d.status & ltrim(str(convert(int, 0x03e0), 11))  = 0)' +  
   N' and ((DATABASEPROPERTY(d.name, ''issingleuser'') = 0 and (has_dbaccess(d.name) = 1)) or ' +  
   N' ( DATABASEPROPERTY(d.name, ''issingleuser'') = 1 and not exists ' +  
   N' (select * from master.dbo.sysprocesses p where dbid = d.dbid and p.spid <> @@spid)))' )
exec sp_Msforeach_worker @command1="print '?'",@command2="dbcc checkdb (?) "

<以上是被隐藏的代码>

言归正传,下面开始写如何进行数据库还原:

1.我们之所以无法在程序里无法进行数据库还原操作,是因为我们自己在访问数据库,或者有别的用户在访问着我们要还原的数据库,这种情况下,我们很自然的就想到了用关闭掉用户连接的方法来实现我们的数据库还原操作.那么,如何关闭掉用户的连接呢?

2.关闭用户连接,也就是杀死相应的进程标识.在SQL SERVER里,我们可以通过master库里的kill + 进程ID 语句来杀掉某个进程.此时,我们就应该想办法来取出和我们要还原的数据库的相关进程ID.假设我们要还原的数据库名叫"testRestore",那么,我们可以通过select spid from master.dbo.sysprocesses where dbid=db_id('testRestore');语句来获取和testRestore数据库相关的进程ID,此时它获得的是一个记录集,即有几个连接用户,它就会有几条记录.

3.取出记录集后,我们很自然地就想到了要用游标来实现通过循环来杀死进程的方法.此时,我们就通过刚才说的sql server未公开的存储过程sp_msforeach_worker来实现此操作.

4.根据sp_msforeach_worker游标操作存储过程,我们写出如下语句来杀死所有与testRestore连接的进程:

--杀死所有与testRestore连接进程
declare hcforeach cursor global for select 'kill '+rtrim(spid) from master.dbo.sysprocesses
where dbid=db_id('testRestore');--声明并生成一个游标,取得所有与testRestore相关联的进程ID
exec sp_msforeach_worker'?'    --运行sp_msforeach_worker存储过程,执行杀死进程的过程

5.此时杀死了进程,我们就可以按照正常的还原数据库的语句开始进行还原了.

--进行数据库还原

restore database testRestore from disk='d:/test.bak';

6.总结:关于这个数据库还原问题,从我开始学习asp做数据库备份与还原时就一直困扰着我.今天终于把它搞定了!当然,以上几点只是把方法给大概说了一下,真正做起来,我觉得我们最好还是把"杀掉连接进程"与"数据库还原"语句写成一个master库的存储过程,然后传入一个数据库备份地址参数,此时,仅需要调用此存储过程,只要传入的备份是一个正确的备份,那么,无论有人在访问还是无人在访问,我们均可以正常地还原数据库了.