CODEWITHSUNDEEP
sql-serversql-server-2012relationshipforeign-key-relationship
Samantha J T Star
Samantha J T Star

Reputation: 32828

How can I set up my SQL so that a delete on a parent deletes child rows?

I am using SQL Server 2012 and I have the following DDL:

CREATE TABLE [dbo].[Test] (
    [TestId]       INT            IDENTITY (1, 1) NOT NULL,
    [Title]        NVARCHAR (100) NULL,
    CONSTRAINT [PK_Test] PRIMARY KEY CLUSTERED ([TestId] ASC)
);

CREATE TABLE [dbo].[TestQuestion] (
    [TestId]         INT      NOT NULL,
    [TestQuestionId] INT      NOT NULL,
    [QuestionUId]    CHAR (6) NOT NULL,
    CONSTRAINT [PK_TestQuestion] PRIMARY KEY CLUSTERED ([TestId] ASC, [TestQuestionId] ASC),
    CONSTRAINT [FK_TestQuestionTest] FOREIGN KEY ([TestId]) REFERENCES [dbo].[Test] ([TestId])
);

Is there a way I can make this so that when I delete a row in the Test table then all rows with that TestId are deleted from the TestQuestion table?

Upvotes: 0

Views: 47

Answers (2)

Ash8087
Ash8087

Reputation: 701

As other commentators have said, the cascading foreign key is the best way to go. If you need more complicated logic, however, you could use a FOR DELETE trigger.

Upvotes: 0

NiiL
NiiL

Reputation: 2827

just provide ON DELETE CASCADE to your Foreign Key of Child Table(TestQuestion.TestId), so it will delete child record directly when parent record is deleted.

CREATE TABLE [dbo].[Test] (
        [TestId]       INT            IDENTITY (1, 1) NOT NULL,
        [Title]        NVARCHAR (100) NULL,
        CONSTRAINT [PK_Test] PRIMARY KEY CLUSTERED ([TestId] ASC)
    );

    CREATE TABLE [dbo].[TestQuestion] (
        [TestId]         INT      NOT NULL,
        [TestQuestionId] INT      NOT NULL,
        [QuestionUId]    CHAR (6) NOT NULL,
        CONSTRAINT [PK_TestQuestion] PRIMARY KEY CLUSTERED ([TestId] ASC, [TestQuestionId] ASC),
        CONSTRAINT [FK_TestQuestionTest] FOREIGN KEY ([TestId]) REFERENCES [dbo].[Test] ([TestId]) ON DELETE CASCADE
    );

Actually you can have many option with DELETE (and UPDATE also) like:

.

For Delete

ON DELETE { NO ACTION | CASCADE | SET NULL | SET DEFAULT }

.

For Update

ON UPDATE { NO ACTION | CASCADE | SET NULL | SET DEFAULT }

Upvotes: 2

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