主键的 SQL 外键问题

Question

我在 MSSQL Management Studio 上连接两个表时遇到问题。 我的目标是通过外键连接表，如果我删除用户，我希望第二个表条目将被自动删除。我打算为此使用 DELETE Cascade 方法。

User:
CREATE TABLE [dbo].[Users](
[ID] [bigint] IDENTITY(1,1) NOT NULL,
[Email] [nvarchar](89) NOT NULL,
[Name] [nvarchar](25) NOT NULL,
[Midname] [nvarchar](25) NOT NULL,
[Surname] [nvarchar](25) NOT NULL,
[Phone] [varchar](15) NOT NULL,
[Country] [smallint] NOT NULL,
[Manager] [nvarchar](89) NOT NULL,
[Referrer] [nvarchar](89) NOT NULL,
[Rank] [tinyint] NOT NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED 
(
[Email] 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

电子邮件是主键

Payments:
 CREATE TABLE [dbo].[Investments](
[ID] [bigint] NOT NULL,
[Investor] [nvarchar](89) NOT NULL,
[Sum] [decimal](19, 4) NOT NULL,
[Currency] [smallint] NOT NULL,
[Credit] [decimal](19, 4) NOT NULL,
[CreditRate] [decimal](19, 4) NOT NULL,
[Rate] [tinyint] IDENTITY(1,1) NOT NULL,
[Date] [smalldatetime] NOT NULL,
[Comment] [nvarchar](max) NOT NULL,
CONSTRAINT [PK_Investments] 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

ID 是主键

我的 FK 应该是 USER->PAYMENTS 还是 PAYMENTS->USER？

当我尝试连接用户 -> 通过电子邮件使用外键付款 -> 投资者时，它告诉我这样的错误：

“Payments”表中的列与现有主键或 UNIQUE 约束不匹配。

你能解释一下问题出在哪里吗？而我做错了什么？

Answer 1

将结构更改为：

CREATE TABLE [dbo].[Users](
[ID] [bigint] IDENTITY(1,1) NOT NULL,
[Email] [nvarchar](89) NOT NULL,
[Name] [nvarchar](25) NOT NULL,
[Midname] [nvarchar](25) NOT NULL,
[Surname] [nvarchar](25) NOT NULL,
[Phone] [varchar](15) NOT NULL,
[Country] [smallint] NOT NULL,
[Manager] [nvarchar](89) NOT NULL,
[Referrer] [nvarchar](89) NOT NULL,
[Rank] [tinyint] NOT NULL);

ALTER TABLE [Users]
ADD CONSTRAINT PK_UsersID PRIMARY KEY (ID);

然后

CREATE TABLE [dbo].[Investments](
[ID] [bigint] NOT NULL,
[UserID] [bigint] NOT NULL,
[Sum] [decimal](19, 4) NOT NULL,
[Currency] [smallint] NOT NULL,
[Credit] [decimal](19, 4) NOT NULL,
[CreditRate] [decimal](19, 4) NOT NULL,
[Rate] [tinyint] IDENTITY(1,1) NOT NULL,
[Date] [smalldatetime] NOT NULL,
[Comment] [nvarchar](max) NOT NULL);

ALTER TABLE Investments
ADD CONSTRAINT PK_InstestmentsID PRIMARY KEY (ID);

ALTER TABLE Investments
ADD CONSTRAINT FK_UsersInvestments
FOREIGN KEY (UserID)
REFERENCES Users(ID);

然后加入Users.IDInvestments.UserID

Answer 2

我搜索了您看到的错误消息（没有表名）和普遍共识 似乎您的表格中没有正确设置PRIMARY KEY 或UNIQUE 约束。该错误还告诉我您（可能）正在使用 SQL Server。

来自technet.microsoft.com：

外键关系的主键端的列必须 参与主键或唯一约束。后 为其中一个表设置主键或唯一约束 您已选择，然后您可以为此定义其他关系 表。

在两个表中检查您的PRIMARY KEYS。如果没有表的实际 DDL，就很难提供更多帮助。

编辑：您在Users 表中有Email 作为PRIMARY KEY，但我在Investments 表中看不到Email 字段。您要加入哪些领域？