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  1. #1
    Join Date
    Aug 2010
    Posts
    3

    DB design, a few issues.

    I've been developing for someone, I'm new so it's all free thus it's for experience only. I say that because you'll likely notice lots of errors here that I'm not aware off and boil your blood because someone could be profiting off such tripe!

    anyway:

    They're the bulk of my tables, it's all important.

    http://i.imgur.com/8wbL4.jpg

    I'm having trouble deciding the relationships. Here's what I think you should know:

    A customer can only be an exhibitor, trader, food vendor or weekender.
    A customer cannot be more than one of the above.
    The aforementioned can only be one registered customer even if they bring x amount of staff.

    That tells me it's a simple 1-1 relationship. At first I thought they were 1-n but I'm convinced they should be 1-1. If I create a form I get a lot of errors, although 1-n worked fine when I had that set up (you'll notice multiple IDs).

    The reason I've kept customer types separate and not just included a field determining the customer type is because different data is stored depending on the customer type.

    So, am I handling this the right way? or do I have my wires crossed?

    thanks.

  2. #2
    Join Date
    Apr 2002
    Location
    Toronto, Canada
    Posts
    20,002
    do a search for supertype/subtype -- i believe you are on the right track

    well, except for the additional id columns (foodvendorid, etc.) that you are assigning to customers



    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  3. #3
    Join Date
    Jul 2008
    Posts
    7
    I see it alright, although those address lines seem kind of suspicious. You may have to normalize some tables a little, so I recommend you to read about normalization as well as what r937 told you.

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