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浅析SQL Server 一个没有公开的存储过程


  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.
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