У меня есть три таблицы a, b и c, каждая с полем int IDENTITY PK, которое относится к дочерней таблице.УНИКАЛЬНОЕ ограничение для столбцов на разных таблицах
CREATE TABLE [dbo].[a]([aID] [int] IDENTITY(1,1) NOT NULL,[aCode] [varchar](20) NOT NULL,
CONSTRAINT [PK_a] PRIMARY KEY CLUSTERED([aID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
CREATE TABLE [dbo].[b]([bID] [int] IDENTITY(1,1) NOT NULL,[aID] [int] NOT NULL, [bCode] [varchar](20) NOT NULL,
CONSTRAINT [PK_b] PRIMARY KEY CLUSTERED([bID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
CREATE TABLE [dbo].[c]([cID] [int] IDENTITY(1,1) NOT NULL,[bID] [int] NOT NULL,[cCode] [varchar](20) NOT NULL,
CONSTRAINT [PK_c] PRIMARY KEY CLUSTERED([cID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
ALTER TABLE [dbo].[b] WITH CHECK ADD CONSTRAINT [FK_b_a] FOREIGN KEY([aID])
REFERENCES [dbo].[a] ([aID])
GO
ALTER TABLE [dbo].[b] CHECK CONSTRAINT [FK_b_a]
GO
ALTER TABLE [dbo].[c] WITH CHECK ADD CONSTRAINT [FK_c_b] FOREIGN KEY([bID])
REFERENCES [dbo].[b] ([bID])
GO
ALTER TABLE [dbo].[c] CHECK CONSTRAINT [FK_c_b]
GO
Как создать CONSTRAINT, обеспечивающий уникальное условие для a.aID, c.cCode?
Сделать c.cCode уникальным путем добавления уникальных ограничений, a.aID всегда будет уникальным, поскольку это первичный ключ –