Question

在我的数据库中，我有一个Person和Member表。 Member表有2个外键，它们都引用People表中的同一列。约束如下所示：

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.

我将如何解决这个问题？

基本上这是我试图获得的行为：

删除PersonID引用的记录。我需要它删除其他表中的所有子记录。（那里有8个子表）
删除EnquiryTakenBy引用的记录时。我需要将EnquiryTakenBy设置为null。

编辑：表格结构如下：

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

)

Answer 1

好的，找到了解决方案。显然我的问题与SQL Server有关，并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

如何解决多个级联路径？

1 个答案: