我有这个表在外键列中设置空值?
CREATE TABLE [dbo].[CityMaster](
[CityID] [int] NOT NULL,
[City] [varchar](100) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[BranchId] [varchar](10) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL CONSTRAINT [DF__CityM__Branc__74444068] DEFAULT ((0)),
[ExternalBranchId] [varchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
CONSTRAINT [PK_CityMaster] PRIMARY KEY CLUSTERED
(
[City] ASC,
[BranchId] ASC
),
CONSTRAINT [uk_citymaster_cityid_branchid] UNIQUE NONCLUSTERED
(
[CityID] ASC,
[BranchId] ASC
)
)
和另一个表
CREATE TABLE [dbo].[CustomerMaster](
[ID] [int] NOT NULL,
[CustomerCode] [varchar](20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[CustomerName] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[CustomerAddress] [varchar](100) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[CustomerPhone] [varchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[CustomerEmailId] [varchar](100) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[CustomerPriority] [int] NOT NULL CONSTRAINT [DF_CustomerMaster_CustomerPriority] DEFAULT ((0)),
[CustomerRegisterDate] [datetime] NULL,
[CustomerIsActive] [bit] NULL CONSTRAINT [DF_CustomerMaster_CustomerIsActive] DEFAULT ((1)),
[BranchId] [varchar](10) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL CONSTRAINT [DF__CustomerM__Branc__67DE6983] DEFAULT ((0)),
[CityId] [int] NULL CONSTRAINT [DF_CustomerMaster_CityId] DEFAULT ((0)),
CONSTRAINT [PK_CustomerMaster] PRIMARY KEY CLUSTERED
(
[CustomerCode] ASC,
[BranchId] ASC
)
) ON [PRIMARY]
ALTER TABLE [dbo].[CustomerMaster] WITH CHECK ADD CONSTRAINT [fk_cdCityId_CityId] FOREIGN KEY([CityId], [BranchId])
REFERENCES [dbo].[CityMaster] ([CityID], [BranchId])
ALTER TABLE [dbo].[CustomerMaster] CHECK CONSTRAINT [fk_cdCityId_CityId]
正如你所看到的,对CityId, BranchId
外键。我遇到的问题是,如果用户没有进入他的城市(他可以选择不这样做,这个字段不是强制性的,那么CityId
应该是空白的,当我试图在CustomerMaster
表中插入这个值时,我得到这个错误说
INSERT语句冲突与外键约束“fk_cdCityId_CityId”。该冲突发生于数据库“TestDatabase”,表“dbo.CityMaster”。 该语句已终止。
所以,我想知道一种解决这个问题的方法,我知道如果一个唯一或主键列被引用为外键,它不能为空。但是,当我设置了 on delete set null
?在这种情况下,如果该行从CityMaster
中删除,它将被设置为null
的CustomerMaster
(我的意思是它的所有参考)。所以,如果这是可能的,为什么以及如何手动设置这个外键null
的值? 如果无法做到这一点,那么规避我所描述的情况的最好办法是什么?
@达明最不信: 所以,我应该删除这个'默认值(0)'条款? – Razort4x
@ Razort4x - 我会这么说,是的。 –
不错,它没有帮助我 –