mysql - 将外键从多对多关系导出到另一个表sql

Question

我有一张 table

CREATE TABLE [dbo].[CoursesOfferedToBatches] (
    [CourseId] VARCHAR (50) NOT NULL,
    [Batch]    INT          NOT NULL,
    PRIMARY KEY CLUSTERED ([Batch] ASC, [CourseId] ASC),
    CONSTRAINT [FK_OfferedCourses_ToCourses] FOREIGN KEY ([CourseId]) REFERENCES [dbo].[Courses] ([Id]),
    CONSTRAINT [FK_CoursesOfferedToBatches_ToBatches] FOREIGN KEY ([Batch]) REFERENCES [dbo].[Batches] ([Id])
);

当我将 CourseId 作为外键从上表导出到下表时，如下所示，它在表后给出如下所示的错误

CREATE TABLE [dbo].[StudentsRegisterToCoursesOffered]
(
    [StudentId] UNIQUEIDENTIFIER NOT NULL , 
    [CourseId] VARCHAR(50) NOT NULL, 
    PRIMARY KEY ([CourseId], [StudentId]), 
    CONSTRAINT [FK_StudentsRegisterToCoursesOffered_ToStudents] FOREIGN KEY ([StudentId]) REFERENCES [Students]([StudentId]), 
    CONSTRAINT [FK_StudentsRegisterToCoursesOffered_ToCoursesOffered] FOREIGN KEY ([CourseId]) REFERENCES [CoursesOfferedToBatches]([CourseId])
)

错误:

Update cannot proceed due to validation errors. Please correct the following errors and try again.

SQL71516 :: The referenced table '[dbo].[CoursesOfferedToBatches]' contains no primary or candidate keys that match the referencing column list in the foreign key. If the referenced column is a computed column, it should be persisted.

我的问题到此结束，但为了引用，我添加了所有相关表格:

CREATE TABLE [dbo].[Courses] (
    [Id]   VARCHAR (50)  NOT NULL,
    [Name] VARCHAR (100) NOT NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);


CREATE TABLE [dbo].[Students] (
    [StudentId]      UNIQUEIDENTIFIER NOT NULL,
    [DepartmentName] VARCHAR (50)     NOT NULL,
    [Address]        VARCHAR (250)    NULL,
    [TwitterLink]    VARCHAR (100)    NULL,
    [FacebookLink]   VARCHAR (100)    NULL,
    [MemberSince]    DATETIME         NULL,
    [ProfileViews]   BIGINT           DEFAULT ((0)) NULL,
    [CNIC]           CHAR (15)        NULL,
    [AboutMe]        VARCHAR (3000)   NULL,
    PRIMARY KEY CLUSTERED ([StudentId] ASC),
    CONSTRAINT [FK_Students_ToStudents] FOREIGN KEY ([StudentId]) REFERENCES [dbo].[Users] ([UserId]),
    CONSTRAINT [FK_Students_ToDepartments] FOREIGN KEY ([DepartmentName]) REFERENCES [dbo].[Departments] ([Name])
);


CREATE TABLE [dbo].[Batches] (
    [Id] INT NOT NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

Answer 1

表 CoursesOfferedToBatches 需要有自己的主键，您已将其创建为复合键 PRIMARY KEY CLUSTERED ([Batch] ASC, [CourseId] ASC) .正是这个复合键将成为 StudentsRegisterToCoursesOffered 中的外键，而不仅仅是 CourseId。