如何取消外键约束 [英] How to Drop Foreign Key Constraint

问题描述

大家好，

谁能告诉我如何在sql中删除在列级别定义的外键约束(或者我们可以说没有名字).

代码示例:

Hi All,

Would anyone please tell me how to drop a foreign key constraint defined on column level in sql(or we can say having no name).

Code Example:

Create Table Employee
(
Employee_ID int Primary Key,
Job_ID int Foreign Key references JOB(Job_ID)  
)

/*考虑到另一个名为"JOB"的表，该表的列为Job-ID */

/*consider there is another table Named "JOB" with column Job-ID*/

推荐答案

您不能删除该列，因为它依赖于另一列，但是您可以从列中删除密钥.对象资源管理器->扩展表格->键->右键单击->删除

You can''t drop the column because it depends on another column, but you can remove the key from the column. object explorer->expand your table->keys->right click->delete

创建表[dbo].[t3](
[id] [int] NOT NULL，
[n_id] [int] NULL，
约束[PK_t3]主键簇
(
[id] ASC
)与(PAD_INDEX = OFF，STATISTICS_NORECOMPUTE = OFF，IGNORE_DUP_KEY = OFF，ALLOW_ROW_LOCKS = ON，ALLOW_PAGE_LOCKS = ON)一起使用[PRIMARY]
)于[PRIMARY]

GO

创建表[dbo].[t3](
[id] [int] NOT NULL，
[n_id] [int] NULL，
约束[PK_t3]主键簇
(
[id] ASC
)与(PAD_INDEX = OFF，STATISTICS_NORECOMPUTE = OFF，IGNORE_DUP_KEY = OFF，ALLOW_ROW_LOCKS = ON，ALLOW_PAGE_LOCKS = ON)一起使用[PRIMARY]
)于[PRIMARY]

GO

带有检查添加约束[FK_t3_t2]外键([id])
的ALTER TABLE [dbo].[t3] 参考[dbo].[t2]([n_id])
GO

更改表放置约束FK_t3_t2

CREATE TABLE [dbo].[t3](
[id] [int] NOT NULL,
[n_id] [int] NULL,
CONSTRAINT [PK_t3] PRIMARY KEY CLUSTERED
(
[id] 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].[t3](
[id] [int] NOT NULL,
[n_id] [int] NULL,
CONSTRAINT [PK_t3] PRIMARY KEY CLUSTERED
(
[id] 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].[t3] WITH CHECK ADD CONSTRAINT [FK_t3_t2] FOREIGN KEY([id])
REFERENCES [dbo].[t2] ([n_id])
GO

alter table drop constraint FK_t3_t2

更改表雇员放置Employee_Job_ID

alter table Employee drop Employee_Job_ID

这篇关于如何取消外键约束的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！