Question

我有这些表格：

CREATE TABLE [dbo].[ObjectiveDetail] (
    [ObjectiveDetailId] INT            IDENTITY (1, 1) NOT NULL,
    [ObjectiveId]       INT            NOT NULL,
    [Number]            INT            NOT NULL,
    [Text]              NVARCHAR (MAX) NOT NULL,
    CONSTRAINT [PK_ObjectiveDetail] PRIMARY KEY CLUSTERED ([ObjectiveDetailId] ASC),
    CONSTRAINT [FK_ObjectiveDetailObjective] FOREIGN KEY ([ObjectiveId]) REFERENCES [dbo].[Objective] ([ObjectiveId])
);

CREATE TABLE [dbo].[ObjectiveTopic] (
    [ObjectiveDetailId] INT NOT NULL,
    [SubTopicId]        INT NOT NULL,
    CONSTRAINT [PK_ObjectiveTopicObjectiveDetail] PRIMARY KEY CLUSTERED ([ObjectiveDetailId] ASC, [SubTopicId] ASC),
    CONSTRAINT [FK_ObjectiveTopicObjectiveDetail] FOREIGN KEY ([ObjectiveDetailId]) REFERENCES [dbo].[ObjectiveDetail] ([ObjectiveDetailId]),
    CONSTRAINT [FK_ObjectiveTopicSubTopic] FOREIGN KEY ([SubTopicId]) REFERENCES [dbo].[SubTopic] ([SubTopicId])
);


GO
CREATE UNIQUE NONCLUSTERED INDEX [NobjectiveDetail_Number_IX]
    ON [dbo].[ObjectiveDetail]([ObjectiveId] ASC, [Number] ASC);


GO
CREATE NONCLUSTERED INDEX [Objective_ObjectiveDetailId_IX]
    ON [dbo].[ObjectiveDetail]([ObjectiveDetailId] ASC);

我想要做的是删除一个ObjectiveDetail。但是如果ObjectiveTopic表中有一行，则删除失败。

当ObjectiveDetail行被删除时，是否还有一些方法可以删除ObjectiveTopic表中的另一行？

Answer 1

更改约束，使其启用ON DELETE CASCADE。

ALTER TABLE dbo.LocalData
   DROP CONSTRAINT FK_ReferenceDataLocaldata 

ALTER TABLE dbo.LocalData
   ADD CONSTRAINT FK_ReferenceDataLocaldata_Cascade
  FOREIGN KEY (ForeignID) REFERENCES dbo.ReferenceData(ForeignPK) ON DELETE CASCADE

基本上你所做的就是在添加约束命令

的末尾添加ON DELETE CASCADE

要将此问题应用于您的问题，我们需要更改

ALTER TABLE ObjectiveTopic
DROP CONSTRAINT [FK_ObjectiveTopicObjectiveDetail]

到

ALTER TABLE ObjectiveTopic
CREATE CONSTRAINT [FK_ObjectiveTopicObjectiveDetail] FOREIGN KEY ([ObjectiveDetailId]) REFERENCES [dbo].[ObjectiveDetail] ([ObjectiveDetailId]) ON DELETE CASCASE

Answer 2

ALTER TABLE dbo.ReferenceData DROP CONSTRAINT FK_MyTable

ALTER TABLE dbo.LocalData 
   ADD CONSTRAINT FK_ReferenceDataLocaldata_Cascade 
   FOREIGN KEY (ForeignID) REFERENCES dbo.ReferenceData(ForeignPK) 
   ON DELETE CASCADE

我怎么能这样做，以便即使在另一个表中有外键和行时我也可以删除它？

2 个答案: