删除员工与部门经理外键约束冲突

Question

我创建了两个 table 部门和员工，结构如下：

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

有些现有员工已经是部门 table 的经理，现在当我尝试删除任何这些经理员工时，我收到外键约束冲突错误，阻止删除语句。请问有什么问题吗？

Answer 1

问题是您不允许这样做。

外键约束是一种完整性约束，这意味着它确保跨 table 的数据完整性。

如果某一部门行说这个部门的经理的员工ID是73，如果数据库中没有ID为73的员工就不好了。

外键约束可确保不会发生这种情况：

您不能插入或更新部门行以具有员工中不存在的经理 ID table
您不能从部门行中删除被引用为经理的员工
您不能更新从部门行引用为经理的员工的 ID

解决方法是首先通过以下方式修复部门：

通过更新部门行和调整经理的 ID 切换到不同的经理
NULL'ing out the manager，说这个部门没有经理，如果允许的话

在执行这两个操作中的任何一个之后，假设没有其他外键引用，您应该能够删除该员工。

删除员工与部门经理外键约束冲突

deleting an employee conflicts with department manager foreign key constraint

database

sql-server

foreign-key-relationship