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浅析SQL SERVER一个没有公开的存储过程

  【IT168 服务器学院】从SQLSERVER6.5开始,MS提供了一个非常有用的系统存储过程sp_MSforeachtable和sp_MSforeachDB;作为DBA会经常需要检查所有的数据库或用户表,比如:检查所有数据库的容量;看看指定数据库所有用户表的容量,所有表的记录数...,我们一般处理这样的问题都是用游标分别处理处理,比如:在数据库检索效率非常慢时,我们想检查数据库所有的用户表,我们就必须这样写游标:
  DECLARE @TableName varchar(255)
  DECLARE @ExeSQL varchar(4000)

  DECLARE Table_Cursor CURSOR FOR SELECT [name] FROM sysobjects WHERE xtype=''U''

  OPEN Table_Cursor
  FETCH NEXT FROM  Table_Cursor INTO @TableName

  WHILE(@@FETCH_STATUS=0)
  BEGIN
   PRINT @TableName
   SELECT @ExeSQL=''DBCC CHECKTABLE(''''+@TableName+'''')''
   EXEC(@EXESQL)
  FETCH NEXT FROM  Table_Cursor INTO @TableName
  END

  CLOSE Table_Cursor
  DEALLOCATE Table_Cursor
  GO

  如果我们用sp_MSforeachtable就可以非常方便的达到相同的目的:
  EXEC sp_MSforeachtable @command1="print ''?'' DBCC CHECKTABLE(''?'')"
  大家可以看出这样就更加简洁(虽然在后台也是通过游标来处理的),下面我们就仔细分析一下sp_MSforeachtable这个存储过程:

  我们看看sp_MSforeachtable详细的CODE:
  USE MASTER
  GO
  SP_HELPTEXT sp_MSforeachtable

  --下面时sp_MSforeachtable的原始代码

  CREATE proc sp_MSforeachtable
   @command1 nvarchar(2000), @replacechar nchar(1) = N''?'', @command2 nvarchar(2000) = null,
     @command3 nvarchar(2000) = null, @whereand nvarchar(2000) = null,
   @precommand nvarchar(2000) = null, @postcommand nvarchar(2000) = null
  as
   /* This proc returns one or more rows for each table (optionally, matching @where), with each table defaulting to its

  own result set */
   /* @precommand and @postcommand may be used to force a single result set via a temp table. */

   /* Preprocessor won''t replace within quotes so have to use str(). */
   declare @mscat nvarchar(12)
   select @mscat = ltrim(str(convert(int, 0x0002)))

   if (@precommand is not null)
    exec(@precommand)

   /* Create the select */
     exec(N''declare hCForEach cursor global for select ''['' + REPLACE(user_name(uid), N'']'', N'']]'') + '']'' + ''.'' + ''[''

  + REPLACE(object_name(id), N'']'', N'']]'') + '']'' from dbo.sysobjects o ''
           + N'' where OBJECTPROPERTY(o.id, N''IsUserTable'') = 1 '' + N'' and o.category & '' + @mscat + N'' = 0 ''
           + @whereand)
   declare @retval int
   select @retval = @@error
   if (@retval = 0)
    exec @retval = sp_MSforeach_worker @command1, @replacechar, @command2, @command3

   if (@retval = 0 and @postcommand is not null)
    exec(@postcommand)

   return @retval

  这个系统存储过程有7个参数:
   @command1 nvarchar(2000),  --第一条运行的T-SQL指令
   @replacechar nchar(1) = N''?'',   --指定的占位符号
   @command2 nvarchar(2000) = null,--第二条运行的T-SQL指令
      @command3 nvarchar(2000) = null, --第三条运行的T-SQL指令
   @whereand nvarchar(2000) = null, --可选条件来选择表
   @precommand nvarchar(2000) = null, --在表前执行的指令
   @postcommand nvarchar(2000) = null --在表后执行的指令

  
  所以上面的语句也可以这样写:
  EXEC sp_MSforeachtable @command1="print ''?''",
           @command2= "DBCC CHECKTABLE(''?'')"

  了解参数以后,就让我们做几个实列吧:
  1.获得每个表的记录数和容量:
  EXEC sp_MSforeachtable @command1="print ''?''",
           @command2="sp_spaceused ''?''",
           @command3= "SELECT count(*) FROM ? "

  2.更新PUBS数据库中已t开头的所有表的统计:
  EXEC sp_MSforeachtable @whereand="and name like ''t%''",
           @replacechar=''*'',
           @precommand="print ''Updating Statistics.....'' print ''",
           @command1="print ''*'' update statistics * ",
           @postcommand= "print''print ''Complete Update Statistics!''"

  
  sp_MSforeachDB除了@whereand外,和sp_MSforeachtable的参数是一样的,我们可以通过这个存储过程检测所有的数据库,比如:
  1.获得所有的数据库的存储空间:
         EXEC sp_MSforeachdb  @command1="print ''?''",
                                           @command2="sp_spaceused "
  2.检查所有的数据库
         EXEC sp_MSforeachdb  @command1="print ''?''",
                                             @command2="DBCC CHECKDB (?) "

  有了上面的分析,我们可以建立自己的sp_MSforeachObject:
  USE MASTER
  GO
  CREATE proc sp_MSforeachObject
   @objectType int=1,
   @command1 nvarchar(2000),
   @replacechar nchar(1) = N''?'',
   @command2 nvarchar(2000) = null,
      @command3 nvarchar(2000) = null,
   @whereand nvarchar(2000) = null,
   @precommand nvarchar(2000) = null,
   @postcommand nvarchar(2000) = null
  as
   /* This proc returns one or more rows for each table (optionally, matching @where), with each table defaulting to its

  own result set */
   /* @precommand and @postcommand may be used to force a single result set via a temp table. */

   /* Preprocessor won''t replace within quotes so have to use str(). */
   declare @mscat nvarchar(12)
   select @mscat = ltrim(str(convert(int, 0x0002)))

   if (@precommand is not null)
    exec(@precommand)

   /* Defined  @isobject for save object type */
   Declare @isobject varchar(256)

   select @isobject= case @objectType when 1 then ''IsUserTable''
           when 2 then ''IsView''
           when 3 then ''IsTrigger''
           when 4 then ''IsProcedure''
           when 5 then ''IsDefault''  
           when 6 then ''IsForeignKey''
           when 7 then ''IsScalarFunction''
           when 8 then ''IsInlineFunction''
           when 9 then ''IsPrimaryKey''
           when 10 then ''IsExtendedProc''   
           when 11 then ''IsReplProc''
           when 12 then ''IsRule''
                    end

   /* Create the select */
   /* Use @isobject variable isstead of IsUserTable string */
  EXEC(N''declare hCForEach cursor global for select ''['' + REPLACE(user_name(uid), N'']'', N'']]'') + '']'' + ''.'' + ''['' +

  REPLACE(object_name(id), N'']'', N'']]'') + '']'' from dbo.sysobjects o ''
          + N'' where OBJECTPROPERTY(o.id, N''''+@isobject+'''') = 1 ''+N'' and o.category & '' + @mscat + N'' = 0 ''
         + @whereand)

   declare @retval int
   select @retval = @@error
   if (@retval = 0)
    exec @retval = sp_MSforeach_worker @command1, @replacechar, @command2, @command3

   if (@retval = 0 and @postcommand is not null)
    exec(@postcommand)

   return @retval

  GO
  这样我们来测试一下:
  1.获得所有的存储过程的脚本:
           EXEc sp_MSforeachObject @command1="sp_helptext ''?'' ",@objectType=4
  2.获得所有的视图的脚本:
           EXEc sp_MSforeachObject @command1="sp_helptext ''?'' ",@objectType=2
  3.比如在开发过程中,没一个用户都是自己的OBJECT OWNER,所以在真实的数据库时都要改为DBO:
             EXEc sp_MSforeachObject @command1="sp_changeobjectowner ''?'', ''dbo''",@objectType=1
             EXEc sp_MSforeachObject @command1="sp_changeobjectowner ''?'', ''dbo''",@objectType=2
              EXEc sp_MSforeachObject @command1="sp_changeobjectowner ''?'', ''dbo''",@objectType=3
                EXEc sp_MSforeachObject @command1="sp_changeobjectowner ''?'', ''dbo''",@objectType=4
    这样就非常方便的将每一个数据库对象改为DBO.

  当然还要很多非常好的功能,大家可以自己深入研究吧:-)

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