[Last Call] Learn how to a build a cloud-first strategyRegister Now

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 367
  • Last Modified:

Optional Foreign Key Constraints?

There are three tables: bugs, comments and attachments.

A comment is always associated with a bug. (bugs have comments).

An attachment will always be associated with a comment (attachments belong to specific comments)

BUT a comment will not always have an attachment. (Like cookies, attachments are a sometimes food).

How do I setup the foreign key constraints here?

Pretty sure this won't work because if I post a comment without an attachment, it will fail...

CONSTRAINT `fk_comments_bugs1`
    FOREIGN KEY (`comments_bug`)
    REFERENCES `bugreport`.`bugs` (`bugs_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_comments_attachments1`
    FOREIGN KEY (`comments_attachment`)
    REFERENCES `bugreport`.`attachments` (`attachments_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)

Open in new window

0
DrDamnit
Asked:
DrDamnit
1 Solution
 
North2AlaskaCommented:
No, the FK is to prevent you from entering an attachment without a comment.  You should have no problem creating a comment without an attachment.
0
 
Kent OlsenData Warehouse Architect / DBACommented:
Hi DrDamnit,

It's tough to tell from your example, but it sounds like the comments table has a column that contains the attachment ID.  That would be upside down.  The hierarchy should be:

--  Bug Table
--  Comment Table, with the ID of the associated bug.
--  Attachment Table, with the ID of the associated Comment.

That makes both comments and attachments optional, and allows for multiple comments and/or attachments per bug.


Good Luck,
Kent
0

Featured Post

Upgrade your Question Security!

Add Premium security features to your question to ensure its privacy or anonymity. Learn more about your ability to control Question Security today.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now