为复合主键创建外键

Question

我有两个 tables - 教育工作者 和教师:

CREATE TABLE [dbo].[Educators]
(
    [UserId] [nvarchar](128) NOT NULL,
    [FacultyId] [smallint] NOT NULL,
    [InstitutionUserId] [nvarchar](128) NOT NULL,

    CONSTRAINT [PK_Educators] 
        PRIMARY KEY CLUSTERED ([UserId] ASC)
)

CREATE TABLE [dbo].[Faculties]
(
    [InstitutionUserId] [nvarchar](128) NOT NULL,
    [FacultyId] [smallint] NOT NULL,

    CONSTRAINT [PK_UserFaculties] 
        PRIMARY KEY CLUSTERED ([InstitutionUserId] ASC, [FacultyId] ASC)
)

table Faculties 有一个由两列（InstitutionUserId 和 FacultyId）组成的复合主键。我在 Educators table 中也有相同的专栏。我想 link 这两个 table 和一个外键。

所以，这是我的查询：

ALTER TABLE [dbo].[Educators] WITH CHECK 
    ADD CONSTRAINT [FK_Educators_FacultyId_Faculties_FacultyId] 
    FOREIGN KEY ([FacultyId], [InstitutionUserId])
    REFERENCES [dbo].[Faculties] ([FacultyId], [InstitutionUserId])

但我收到此错误消息：

Msg 1776, Level 16, State 0, Line 7
There are no primary or candidate keys in the referenced table 'dbo.Faculties' that match the referencing column list in the foreign key 'FK_Educators_FacultyId_Faculties_FacultyId'.

Msg 1750, Level 16, State 1, Line 7
Could not create constraint or index. See previous errors.

如何解决这个问题？

Answer 1

键的顺序应与定义的顺序相同：

ALTER TABLE dbo.Educators
    ADD CONSTRAINT FK_Educators_FacultyId_Faculties_FacultyId
        FOREIGN KEY(InstitutionUserId, FacultyId)
            REFERENCES dbo.Faculties(InstitutionUserId, FacultyId);

Answer 2

您的表及其约束看起来不错。我能看到的唯一问题是主键中列的顺序

CONSTRAINT [PK_UserFaculties] PRIMARY KEY CLUSTERED 
(
    [InstitutionUserId] ASC,
    [FacultyId] ASC
)

与您在外键约束中声明的顺序不同

ALTER TABLE [dbo].[Educators]  WITH CHECK ADD  CONSTRAINT [FK_Educators_FacultyId_Faculties_FacultyId] FOREIGN KEY([FacultyId], [InstitutionUserId])
REFERENCES [dbo].[Faculties] ([FacultyId], [InstitutionUserId])

尝试像这样更改外键声明中列的顺序：

ALTER TABLE [dbo].[Educators]  WITH CHECK ADD  CONSTRAINT [FK_Educators_FacultyId_Faculties_FacultyId] FOREIGN KEY([InstitutionUserId], [FacultyId])
REFERENCES [dbo].[Faculties] ([InstitutionUserId], [FacultyId])

为复合主键创建外键

Creating a foreign key to compound primary key

sql

tsql

database

sql-server

azure-sql-server