Question

I’m having trouble coming up with a solution for the following issue.

Lets say i have a db that looks something like the following:

Issue Table

Id | Details | CreateDate | ClosedDate

Issue Notes Table

Id | ObjectId | Notes | NoteDate

Issue Assignment Table

Id | ObjectId | AssignedToId| AssignedDate

I’d like allow the linking of an issue to another issue.
I thought about adding a column to the Issue table called ParentIssueId and that would allow me the ability to link issues, but i foresee circular references occurring within the issue table if i go through with this implementation.
Is there a better way to go about doing this, and if so, how?

Thanks

Answer 1

Create a table:

LinkedIssues
IssueIDa    pk composite primary key, fk to Issue table
IssueIDb    pk composite primary key, fk to Issue table

the PK will keep some duplicates away, but create a check constraint: IssueIDa<IssueIDb so you don’t end up with a duplicate like:

row 1 IssueIDa=123
      IssueIDb=987

row 2 IssueIDa=987
      IssueIDb=123

however to prevent a circle like:

row 1 IssueIDa=123
      IssueIDb=987

row 2 IssueIDa=987
      IssueIDb=456

row 3 IssueIDa=456
      IssueIDb=123

you’ll need a trigger that resolves the chain, and fails on a circle. Using a recursive CTE would be your best bet to detect this circle.