为什么使用SQL语句添加用户会出错。

[wangjintao]

我用下面这段语句添加用户，用户是添加成功了。可是db_owner权限就是没有打开。
而且我在删除这个用户的时候，老是提示名称“ASPNET”在USERS中没有找到。
if not exists (select * from master.dbo.syslogins where loginname = N'WANGJINTAO\ASPNET')
exec sp_grantlogin N'WANGJINTAO\ASPNET'
exec sp_defaultdb N'WANGJINTAO\ASPNET', N'MuOnline'
exec sp_defaultlanguage N'WANGJINTAO\ASPNET', N'简体中文'
GO

if not exists (select * from dbo.sysusers where name = N'ASPNET' and uid < 16382)
EXEC sp_grantdbaccess N'WANGJINTAO\ASPNET', N'ASPNET'
GO

exec sp_addrolemember N'db_owner', N'ASPNET'
GO

[zheninchangjiang]

都要加入域名:
use muonline
if not exists (select * from master.dbo.syslogins where loginname = N'WANGJINTAO\ASPNET')
exec sp_grantlogin N'WANGJINTAO\ASPNET'
exec sp_defaultdb N'WANGJINTAO\ASPNET', N'MuOnline'
exec sp_defaultlanguage N'WANGJINTAO\ASPNET', N'简体中文'
GO

if not exists (select * from dbo.sysusers where name = N'WANGJINTAO\ASPNET' and uid < 16382)
EXEC sp_grantdbaccess N'WANGJINTAO\ASPNET', N'ASPNET'
GO

exec sp_addrolemember N'db_owner', N'WANGJINTAO\ASPNET'
GO

[zheninchangjiang]

--作一下修改
use master
go
if not exists (select * from master.dbo.syslogins where loginname = N'WANGJINTAO\ASPNET')
exec sp_grantlogin N'WANGJINTAO\ASPNET'
exec sp_defaultdb N'WANGJINTAO\ASPNET', N'MuOnline'
exec sp_defaultlanguage N'WANGJINTAO\ASPNET', N'简体中文'
GO
use muonline
go
if not exists (select * from dbo.sysusers where name = N'WANGJINTAO\ASPNET' and uid < 16382)
EXEC sp_grantdbaccess N'WANGJINTAO\ASPNET', N'ASPNET'
GO

exec sp_addrolemember N'db_owner', N'WANGJINTAO\ASPNET'
GO