Ниже приведен небольшой пример того, как таблица пользователей может выглядеть с guid в качестве столбца primarykey:
CREATE TABLE [dbo].[Users](
[userId] [uniqueidentifier] NOT NULL,
[Name] [nvarchar](255) NOT NULL,
CONSTRAINT [PK_Users_1] PRIMARY KEY CLUSTERED
(
[userId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[Users] ADD CONSTRAINT [DF_Users_userId] DEFAULT (newid()) FOR [userId]