Question

I’m having a problem with a C# MVC project in ASP.NET.
The problem I have is with a category system: If one category has been added to a company, then you should not be able to add any category that is a parent (higher level in the hierarchy) than what’s already been added (since it’s already included in the search).

Now I have added this in the C# code already using this:

if (companyToUpdate.Category.Any(x => x.Parent.Any(z => z.ID == currentCategoryID))) {
    //already exists
}

Now the problem is that I would like to add this check as a stored procedure in the SQL Server database.

My structure looks like this:

Company (all companies)

 ID Title
1   StackOverflow

Category (all categories)

 ID Title
1   Website
2   Helpful site
3   Very helpful site

CategoryDetails (used to know parent/child of each category,
every category has a relationship to all of its parents)
(Website -> Helpful site -> Very helpful site)

Parent_ID   Child_ID
1           2
1           3
2           3

CompanyCategoryDetails (what categories have been added to this company?)

 Company_ID Category_ID
1           3

Now to the problem:
When you are trying to add a new line (1, 2) into CompanyCategoryDetails, it should be denied, since because you have already added Category_ID 3 to it, that means Category_ID 2 is already included which specified in the CategoryDetails table.

I started doing some check where I INNERJOIN the tables, but didnt get far before I realized it couldnt be done the way I was thinking.

Answer 1

I think the check you are asking for is this:

IF EXISTS(
SELECT * 
FROM    CompanyCategoryDetails CCD
JOIN    CategoryDetails CD
        ON  CCD.Category_ID = CD.Child_ID
WHERE   CCD.Company_ID = @Company_ID
AND     (CD.Parent_ID = @Category_ID OR CD.Child_ID = @Category_ID))
BEGIN
    --already exists
END

This will check for trying to add to a compnay (a) a parent category or (b) an existing category