如何解决多个级联路径？

在我的数据库中，我有一个Person和Member表。 Member表有两个外键，它们都引用People表中的同一列。约束是这样的：如何解决多个级联路径？

CONSTRAINT [FK_Members_People_1] 
    FOREIGN KEY ([PersonID])  
    REFERENCES [People].[People]([ID]) 
    ON DELETE CASCADE 
    ON UPDATE NO ACTION, 

CONSTRAINT [FK_Members_People_2] 
    FOREIGN KEY ([EnquiryTakenBy]) 
    REFERENCES [People].[People]([ID]) 
    ON DELETE SET NULL 
    ON UPDATE NO ACTION

我得到的错误如下：

Introducing FOREIGN KEY constraint 'FK_Members_People_2' on table 'Members' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

我怎么会去解决呢？

基本上这就是我想要得到的行为：

当是PersonID引用的记录被删除。我需要它删除其他表中的所有子记录。（有8个子表）
当EnquiryTakenBy引用的记录被删除时。我需要将EnquiryTakenBy设置为空。

编辑：表结构如下：

CREATE TABLE [People].[People] 
(
    [ID]     INT   NOT NULL IDENTITY, 
    [PersonType]   INT   NOT NULL,   
    [Forename]    VARCHAR(16) NOT NULL, 
    [Surname]    VARCHAR(32) NOT NULL, 
    [Gender]    CHAR(1)  NOT NULL, 
    [DateOfBirth]   DATE   NULL, 
    [HobbiesAndInterests] VARCHAR(256) NULL, 
    [AdditionalInformation] VARCHAR(512) NULL, 
    [LocalCentre]   INT   NOT NULL DEFAULT 0, 

    CONSTRAINT [PK_People] PRIMARY KEY ([ID]), 

    CONSTRAINT [FK_People_PersonType] 
     FOREIGN KEY ([PersonType]) 
     REFERENCES [Lookups].[PersonTypes]([ID]) 
     ON DELETE CASCADE 
     ON UPDATE CASCADE, 

    CONSTRAINT [FK_People_Centres]  
     FOREIGN KEY ([LocalCentre]) 
     REFERENCES [Lookups].[Centres]([ID]) 
     ON DELETE CASCADE 
     ON UPDATE CASCADE 
) 

CREATE TABLE [People].[Members] 
(
    [PersonID]   INT   NOT NULL, 
    [IsActive]   BIT   NOT NULL DEFAULT 0, 
    [Issues]   VARCHAR(500) NULL, 
    [InTreatment]  BIT   NOT NULL DEFAULT 0, 
    [ProblemSubstance] VARCHAR(64) NOT NULL, 
    [WantsHelpWith] VARCHAR(128) NULL, 
    [EnquiryTakenBy] INT   NOT NULL, 
    [IsVolunteer]  BIT   NOT NULL DEFAULT 0, 

    CONSTRAINT [PK_Members] PRIMARY KEY ([PersonID]), 

    CONSTRAINT [FK_Members_People_1] 
     FOREIGN KEY ([PersonID])  
     REFERENCES [People].[People]([ID]) 
     ON DELETE CASCADE 
     ON UPDATE NO ACTION, 

    CONSTRAINT [FK_Members_People_2] 
     FOREIGN KEY ([EnquiryTakenBy]) 
     REFERENCES [People].[People]([ID]) 
     ON DELETE SET NULL 
     ON UPDATE NO ACTION 

)

来源

2015-10-14 Jake

好的，找到了解决办法。显然我的问题是与SQL Server不知道哪个约束优先，所以我用这个触发器替换了第二个外键约束：

CREATE TRIGGER Member_UpdateEnquiryID ON People.People 
AFTER DELETE 
AS 
BEGIN 
    DECLARE @id int = (select id from deleted); 
    UPDATE People.Members 
    SET EnquiryTakenBy = NULL 
    where EnquiryTakenBy = @id 
END

来源

2015-10-14 14:24:59 Jake

如何解决多个级联路径？

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