Linq To Sql进阶系列（二）M:M关系

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[User]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
BEGIN
CREATE TABLE [dbo].[User](
[UserId] [nchar](10) NOT NULL,
[UserName] [nchar](10) NULL,
CONSTRAINT [PK_User] PRIMARY KEY CLUSTERED
(
[UserId] ASC
) ON [PRIMARY]
) ON [PRIMARY]
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[Group]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
BEGIN
CREATE TABLE [dbo].[Group](
[GroupId] [nchar](10) NOT NULL,
[GroupName] [nchar](10) NULL,
CONSTRAINT [PK_Group] PRIMARY KEY CLUSTERED
(
[GroupId] ASC
) ON [PRIMARY]
) ON [PRIMARY]
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[UserInGroup]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
BEGIN
CREATE TABLE [dbo].[UserInGroup](
[UserId] [nchar](10) NOT NULL,
[GroupId] [nchar](10) NOT NULL,
CONSTRAINT [PK_UserInGroup] PRIMARY KEY CLUSTERED
(
[UserId] ASC,
[GroupId] ASC
) ON [PRIMARY]
) ON [PRIMARY]
END
GO
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[FK_UserInGroup_Group]') AND type = 'F')
ALTER TABLE [dbo].[UserInGroup]  WITH CHECK ADD  CONSTRAINT [FK_UserInGroup_Group] FOREIGN KEY([GroupId])
REFERENCES [dbo].[Group] ([GroupId])
GO
ALTER TABLE [dbo].[UserInGroup] CHECK CONSTRAINT [FK_UserInGroup_Group]
GO
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[FK_UserInGroup_User]') AND type = 'F')
ALTER TABLE [dbo].[UserInGroup]  WITH CHECK ADD  CONSTRAINT [FK_UserInGroup_User] FOREIGN KEY([UserId])
REFERENCES [dbo].[User] ([UserId])
GO
ALTER TABLE [dbo].[UserInGroup] CHECK CONSTRAINT [FK_UserInGroup_User]