提问,该怎么解决

提问
本帖最后由 lvjiezi 于 2013-03-22 12:39:57 编辑做练习的时候按照案例输入了公式

declare @data_path nvarchar(256);
set @data_path=(select SUBSTRING(physical_name, 1, charindex(N'master.mdf',LOWER(physical_name))-1)
FROM master.sys.master_files
WHERE DATABASE_PRINCIPAL_ID= 1 AND FILE_ID = 1);
execute('create database demo on primary
(name = arch1,filename = '''+@data_path + 'demodb1.mdf'',size = 100MB, maxsize = 200,
filegrowth = 20),
(name = arch2,filename = '''+@data_path + 'demodb2.ndf'',size = 100mb, maxsize = 200,
filegrowth = 20),
(name = arch3,filename = '''+@data_path + 'demodb3.ndf'',size = 100mb, maxsize = 200,
filegrowth = 20)
log on
(name = archlog1, filename = '''+@data_path + 'archlog1.ldf'',size = 100 mb, maxsize = 200,
filegrowth = 20),
(name = archlog2, filename = '''+@data_path + 'archlog2.ldf'',size = 100 mb, maxsize = 200,
filegrowth = 20)');

检验过程命令可以通过，但是执行的时候提示（列名 'DATABASE_PRINCIPAL_ID' 无效。），想知道出错在那里，还需要哪些前提条件？？

[解决办法]

DECLARE @data_path NVARCHAR(256) ;
SET @data_path = ( SELECT TOP 1
                            SUBSTRING(physical_name, 1,
                                      CHARINDEX(N'master.mdf',
                                                LOWER(physical_name)) - 1)
                   FROM     master.sys.master_files
                   WHERE    DATABASE_PRINCIPAL_ID() = 1
                            AND FILE_ID = 1
                 ) ;
EXECUTE('create database demo on primary
(name = arch1,filename = '''+@data_path + 'demodb1.mdf'',size = 100MB, maxsize = 200,
filegrowth = 20),
(name = arch2,filename = '''+@data_path + 'demodb2.ndf'',size = 100mb, maxsize = 200,
filegrowth = 20),
(name = arch3,filename = '''+@data_path + 'demodb3.ndf'',size = 100mb, maxsize = 200,
filegrowth = 20)
log on 
(name = archlog1, filename = '''+@data_path + 'archlog1.ldf'',size = 100 mb, maxsize = 200, 
 
filegrowth = 20),
(name = archlog2, filename = '''+@data_path + 'archlog2.ldf'',size = 100 mb, maxsize = 200,
filegrowth = 20)') ;

[解决办法]

引用:

按照版主帖子8的最新公式，系统予以通过，我会对照一下两条公式看看能不能理解，不能再问版主，
按照版主
SELECT SUBSTRING(physical_name, 1, LEN(physical_name))
FROM master.sys.master_files
WHERE DATABASE_PRINCIPAL_ID() = 1
AND FILE_ID ……

这个查询是告诉你有多条数据而已，而它的原有查询是先找到每个目前在实例下的数据库存放的路径，然后赋给一个变量，在后面动态生成的时候，写上路径名，也就是说，把新库的mdf、ndf、ldf放在同一个文件夹下，但是万一有几个数据库的存放路径不一样，那么就会报错。
[解决办法]
declare @data_path nvarchar(256);
set @data_path=(select SUBSTRING(physical_name, 1, charindex(N'master.mdf',LOWER(physical_name))-1)
FROM master.sys.master_files
WHERE database_id= 1 AND FILE_ID = 1);
你把DATABASE_PRINCIPAL_ID这个改成database_id就可以了，有时候书上有点错误是正常的啊。
@data_path就就是取数据库的绝对路径的。

提问,该怎么解决

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