Question

我创建了两个具有以下结构的表，部门和员工：

CREATE TABLE [dbo].[departments](
    [department_id] [bigint] IDENTITY(10,10) NOT NULL,
    [department_name] [nvarchar](30) NOT NULL,
    [manager_id] [bigint] NULL,
    [location_id] [bigint] NULL,
    [department_notes] [varchar](150) NULL,
    [created_by] [bigint] NULL,
    [created_date] [datetime] NULL,
    [last_updated_by] [bigint] NULL,
    [last_updated_date1] [datetime] NULL,
    [status] [varchar](12) NOT NULL,
 CONSTRAINT [PK_departments] PRIMARY KEY CLUSTERED 
(
    [department_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
 CONSTRAINT [UQ_NoRepeat] UNIQUE NONCLUSTERED 
(
    [department_name] ASC,
    [location_id] ASC,
    [status] 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

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[departments] ADD  CONSTRAINT [DF_departments_created_date]  DEFAULT (getdate()) FOR [created_date]
GO

ALTER TABLE [dbo].[departments] ADD  CONSTRAINT [DF_departments_created_date1]  DEFAULT (getdate()) FOR [last_updated_date1]
GO

ALTER TABLE [dbo].[departments] ADD  CONSTRAINT [DF_departments_status]  DEFAULT ('Active') FOR [status]
GO

ALTER TABLE [dbo].[departments]  WITH CHECK ADD FOREIGN KEY([manager_id])
REFERENCES [dbo].[employees] ([employee_id])
GO

ALTER TABLE [dbo].[departments]  WITH CHECK ADD  CONSTRAINT [FK_departments_locations] FOREIGN KEY([location_id])
REFERENCES [dbo].[locations] ([location_id])
GO

ALTER TABLE [dbo].[departments] CHECK CONSTRAINT [FK_departments_locations]
GO

ALTER TABLE [dbo].[departments]  WITH CHECK ADD  CONSTRAINT [Ck_deptStatus] CHECK  (([Status]='Deleted' OR [Status]='Active'))
GO

ALTER TABLE [dbo].[departments] CHECK CONSTRAINT [Ck_deptStatus]
GO


CREATE TABLE [dbo].[employees](
    [employee_id] [bigint] NOT NULL,
    [first_name] [nvarchar](20) NULL,
    [last_name] [nvarchar](25) NOT NULL,
    [email] [nvarchar](25) NOT NULL,
    [phone_number] [nvarchar](20) NULL,
    [hire_date] [date] NULL,
    [job_id] [nvarchar](10) NOT NULL,
    [salary] [numeric](8, 2) NOT NULL,
    [commission_pct] [numeric](2, 2) NULL,
    [manager_id] [bigint] NULL,
    [department_id] [bigint] NOT NULL,
    [allow_login] [bit] NOT NULL,
    [user_id] [nvarchar](128) NULL,
    [allow_email] [bit] NOT NULL,
    [driv_lic_no] [nchar](20) NULL,
    [reporting_to] [bigint] NULL,
    [salutation] [nchar](10) NULL,
    [date_of_birth] [date] NULL,
    [gender] [nchar](10) NULL,
    [blood_group] [nchar](10) NULL,
    [Nationality] [nchar](10) NULL,
    [gov_id] [nchar](25) NULL,
    [passport_no] [nchar](25) NULL,
    [passport_expir] [date] NULL,
    [driv_lic_expir] [date] NULL,
    [perm_address] [varchar](250) NULL,
    [perm_city] [varchar](50) NULL,
    [perm_state] [varchar](50) NULL,
    [per_zip] [nchar](20) NULL,
    [perm_country] [nvarchar](6) NULL,
    [current_address] [varchar](250) NULL,
    [current_city] [varchar](50) NULL,
    [current_state] [varchar](50) NULL,
    [current_zip] [nchar](20) NULL,
    [current_country] [nvarchar](6) NULL,
    [mobile_no] [nvarchar](20) NULL,
    [notes] [varchar](250) NULL,
    [added_by] [bigint] NULL,
    [added_on] [date] NULL,
    [send_cred_by_email] [bit] NOT NULL,
    [user_name] [nvarchar](256) NULL,
 CONSTRAINT [PK_employees] PRIMARY KEY CLUSTERED 
(
    [employee_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

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[employees] ADD  CONSTRAINT [DF_employees_allow_login]  DEFAULT ((0)) FOR [allow_login]
GO

ALTER TABLE [dbo].[employees] ADD  CONSTRAINT [DF_employees_allow_email]  DEFAULT ((0)) FOR [allow_email]
GO

ALTER TABLE [dbo].[employees] ADD  DEFAULT ('Mr.') FOR [salutation]
GO

ALTER TABLE [dbo].[employees] ADD  DEFAULT ((1)) FOR [send_cred_by_email]
GO

ALTER TABLE [dbo].[employees]  WITH CHECK ADD  CONSTRAINT [FK_employees_AspNetUsers] FOREIGN KEY([user_id])
REFERENCES [dbo].[AspNetUsers] ([Id])
GO

ALTER TABLE [dbo].[employees] CHECK CONSTRAINT [FK_employees_AspNetUsers]
GO

ALTER TABLE [dbo].[employees]  WITH CHECK ADD  CONSTRAINT [FK_employees_countries] FOREIGN KEY([perm_country])
REFERENCES [dbo].[countries] ([country_id])
GO

ALTER TABLE [dbo].[employees] CHECK CONSTRAINT [FK_employees_countries]
GO

ALTER TABLE [dbo].[employees]  WITH CHECK ADD  CONSTRAINT [FK_employees_countries1] FOREIGN KEY([current_country])
REFERENCES [dbo].[countries] ([country_id])
GO

ALTER TABLE [dbo].[employees] CHECK CONSTRAINT [FK_employees_countries1]
GO

ALTER TABLE [dbo].[employees]  WITH CHECK ADD  CONSTRAINT [FK_employees_employees] FOREIGN KEY([employee_id])
REFERENCES [dbo].[employees] ([employee_id])
GO

ALTER TABLE [dbo].[employees] CHECK CONSTRAINT [FK_employees_employees]
GO

有一些现有员工已经是部门表中的经理，现在当我尝试删除任何这些经理员工时，我得到了一个阻止删除语句的外键约束冲突错误。有什么问题吗？

Answer 1

问题在于你不允许这样做。

外键约束是一种完整性约束，这意味着它可以确保跨表的数据完整性。

如果一个部门行表示该部门经理的员工的ID是73，那么如果数据库中没有ID为73的员工，那就不好了。

外键约束确保不会发生这种情况：

您无法插入或更新部门行以获得员工表中不存在的经理ID
您无法删除从部门行引用为经理的员工
您无法更新从部门行引用为经理的员工的ID

解决方案是先通过以下方式修复部门：

通过更新部门行并调整经理的ID来切换到其他经理
NULL'说出经理，说这个部门没有经理，如果允许的话

在执行这两项操作中的任何一项之后，您应该能够删除该员工，假设没有其他外键引用。

删除员工与部门经理外键约束冲突

1 个答案: