Question

Create foreign key constraint with no check

Asked by: topazg

Dear all,

I am in process of testing installation scripts, and have a problem creating a foreign key constraint with "no check" against it. The following is a snippet from my foreign key constraint building script:

ALTER TABLE [dbo].[product_mailing_region] ADD
      CONSTRAINT [FK_product_mailing_region_product] FOREIGN KEY
      (
            [product_id]
      ) REFERENCES [dbo].[product] (
            [product_id]
      ),
      CONSTRAINT [FK_product_mailing_region_region] FOREIGN KEY
      (
            [region_id]
      ) REFERENCES [dbo].[region] (
            [region_id]
      ),
      CONSTRAINT [FK_product_mailing_region_mailing_type] FOREIGN KEY
      (
            [mailing_type_id]
      ) REFERENCES [dbo].[mailing_type] (
            [mailing_type_id]
      ) NOT FOR REPLICATION
GO

alter table [dbo].[product_mailing_region] nocheck constraint [FK_product_mailing_region_mailing_type]
GO

Now this works fine if there is no data in the database, but it cannot create FK_product_mailing_region_mailing_type in the first place if there is data in the product_mailing_region table without a valid mailing_type_id. How can I incorporate this nocheck attribute into the creation of the foreign key constraint itself?

Best Regards,
- Graham

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Asked On
2007-02-09 at 04:36:02ID22156322
Tags

foreign

,

key

,

constraint

,

check

Topic

MS SQL Server

Participating Experts
1
Points
500
Comments
11

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Answers

 

by: NightmanPosted on 2007-02-09 at 04:46:32ID: 18500788

ALTER TABLE [dbo].[product_mailing_region] WITH NOCHECK ADD
     CONSTRAINT [FK_product_mailing_region_product] FOREIGN KEY
     (
          [product_id]
     ) REFERENCES [dbo].[product] (
          [product_id]
     ),
     CONSTRAINT [FK_product_mailing_region_region] FOREIGN KEY
     (
          [region_id]
     ) REFERENCES [dbo].[region] (
          [region_id]
     ),
     CONSTRAINT [FK_product_mailing_region_mailing_type] FOREIGN KEY
     (
          [mailing_type_id]
     ) REFERENCES [dbo].[mailing_type] (
          [mailing_type_id]
     ) NOT FOR REPLICATION
GO

 

by: NightmanPosted on 2007-02-09 at 04:47:05ID: 18500791

the syntax is

ALTER TABLE tablename WITH NOCHECK ADD Constraint.

 

by: topazgPosted on 2007-02-09 at 05:08:49ID: 18500911

Great, thanks, I've adjusted to:

ALTER TABLE [dbo].[product_mailing_region] ADD
      CONSTRAINT [FK_product_mailing_region_product] FOREIGN KEY
      (
            [product_id]
      ) REFERENCES [dbo].[product] (
            [product_id]
      ),
      CONSTRAINT [FK_product_mailing_region_region] FOREIGN KEY
      (
            [region_id]
      ) REFERENCES [dbo].[region] (
            [region_id]
      )
GO

ALTER TABLE [dbo].[product_mailing_region] WITH NOCHECK ADD
      CONSTRAINT [FK_product_mailing_region_mailing_type] FOREIGN KEY
      (
            [mailing_type_id]
      ) REFERENCES [dbo].[mailing_type] (
            [mailing_type_id]
      ) NOT FOR REPLICATION
GO

So that the NOCHECK only applies to the correct FK constraint. However, the previous syntax also seemed to disable "Enforce relationship for INSERTs and UPDATEs", whereas the new syntax doesn't. How can this be added to the script?

 

by: NightmanPosted on 2007-02-09 at 05:16:05ID: 18500954

>>Enforce relationship for INSERTs and UPDATEs
That is implied already by having the key there already. Unless you want to handle cascades, this should work perfectly well.

 

by: topazgPosted on 2007-02-09 at 06:07:56ID: 18501237

Sorry, I mean how can I disable the "Enforce relationship for INSERTs and UPDATEs" in the script?

 

by: NightmanPosted on 2007-02-09 at 07:01:25ID: 18501650

I'm not sure that you can. But why would you want to? The whole point of a foreign key IS to enforce referential integrity in the first place.

 

by: topazgPosted on 2007-02-09 at 07:07:28ID: 18501710

Yes, the difficulty is having data in there with the value of zero (instead of null) due to the .asp code being designed for multiple database engines and having trouble referencing null in some of them (I forget which, it's probably a legacy problem now anyway).

It's not too much of a hassle, as I can fire the:

alter table [dbo].[product_mailing_region] nocheck constraint [FK_product_mailing_region_mailing_type]
GO

script afterwards anyway, it just seemed odd that they didn't actually set it up in the same way.

So I'm guessing that this is the route I'll have to take to achieve this ?

 

by: NightmanPosted on 2007-02-09 at 07:16:46ID: 18501769

ALTER TABLE product_mailing_region CHECK CONSTRAINT ALL
should do it for you.

 

by: topazgPosted on 2007-02-09 at 07:33:53ID: 18501927

Hmm... it didn't work -- it did the same as the other script, removing the enforce for replication but not the other.

However, running the other script as well works fine, so you've still been extremely helpful

Thanks for your time!

 

by: NightmanPosted on 2007-02-09 at 07:36:34ID: 18501952

It's a pleasure. Good luck with your project.

 

by: topazgPosted on 2007-02-09 at 07:43:18ID: 18502015

Many thanks :)

20120131-EE-VQP-002

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