SQL Server：兩個指向一個表的外鍵。錯誤：將外鍵約束可能會引起循環或多個級聯路徑

我發現了錯誤：SQL Server：兩個指向一個表的外鍵。錯誤：將外鍵約束可能會引起循環或多個級聯路徑

Msg 1785, Level 16, State 0, Line 238
Introducing FOREIGN KEY constraint 'FK_Studios_Members_HeadId' on table 'Studios' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

下面是我有問題的兩個表的簡化版本：

CREATE TABLE [Members] 
(
    [MemberId] int NOT NULL IDENTITY 
) 

CREATE TABLE [Studios] 
(
    [StudioId] int NOT NULL IDENTITY, 
    [HeadId] int, 
    [OwnerId] int, 

    CONSTRAINT [PK_Studios] PRIMARY KEY ([StudioId]), 

    CONSTRAINT [FK_Studios_Members_OwnerId] 
     FOREIGN KEY ([OwnerId]) REFERENCES [Members] ([MemberId]) 
      ON DELETE SET NULL, 
    CONSTRAINT [FK_Studios_Members_HeadId] 
     FOREIGN KEY ([HeadId]) REFERENCES [Members] ([MemberId]) 
      ON DELETE SET NULL 
)

我發現，如果我切換兩個FK的順序，它將始終在第二個錯誤。我不明白爲什麼這會導致級聯問題，因爲它們都具有「ON DELETE SET NULL」。

這是由EF核心代碼生成的，所以我需要這些關係，並且不能在後端的觸發器中進行破解。

我錯過了什麼？

來源

2016-12-01 Alan Shaw

你看到[這]（http://stackoverflow.com/questions/851625/foreign-key-constraint-may-cause-cycles-or-multiple-cascade-paths）？我不知道它是否有助於回答這個問題，但它幫助我理解了一般問題:-) – SMM

好吧，許多可能的重複之一：http://stackoverflow.com/q/21390621/861716 –

我不知道一個答案，將與你在那裏的工作，我不知道你的設計是如何凝固在一起......但作爲替代設計，我不認爲會有同樣的問題你考慮過一個單獨的中間關係表嗎？

這種方法的一個好處是它允許你在每個位置有多個成員。

CREATE TABLE [Members] 
(
    [MemberId] int NOT NULL IDENTITY 
) 

CREATE TABLE [Studios] 
(
    [StudioId] int NOT NULL IDENTITY, 

    CONSTRAINT [PK_Studios] PRIMARY KEY ([StudioId]), 

) 

--Contains Owner, Head, etc. 
CREATE TABLE [Relationships] 
(
    [RelationshipId] int NOT NULL IDENTITY, 
    [RelationshipId] nvarchar(20) NOT NULL 
) 

CREATE TABLE [StudioMemberRelationships] 
(
    [StudioMemberRelationshipId] int NOT NULL IDENTITY, 
    [StudioId] int NOT NULL, 
    [MemberId] int NOT NULL, 
    [RelationshipTypeId] int NOT NULL, 

    CONSTRAINT [FK_StudioMemberRelationships_StudioId] 
     FOREIGN KEY ([StudioId]) REFERENCES [Studios] ([StudioId]) 
      ON DELETE SET NULL, 
    CONSTRAINT [FK_StudioMemberRelationships_MemberId] 
     FOREIGN KEY ([MemberId]) REFERENCES [Members] ([MemberId]) 
      ON DELETE SET NULL, 
    CONSTRAINT [FK_StudioMemberRelationships_RelationshipId] 
     FOREIGN KEY ([RelationshipId]) REFERENCES [Relationships] ([RelationshipId]) 
      ON DELETE SET NULL 
)

來源

2016-12-01 20:19:19 SMM

SQL Server：兩個指向一個表的外鍵。錯誤：將外鍵約束可能會引起循環或多個級聯路徑

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