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.

当然还要很多非常好的功能,大家可以自己深入研究吧:-)