Results 1 to 2 of 2
  1. #1
    Join Date
    Feb 2003

    Question newbie ERD dillema

    I'm building a database to track laptop hotswaps (i.e. defective laptop gets traded immediately for in-stock refurb of same type, then gets repaired after-the-fact and put back into stock for the next hotswap). I WILL have more questions later about the structure of the actual hotswap activity tracking table, but that'll come later...
    For now, I just need help with accurately modeling laptop types:

    My attributes are Make, Model, ModelNumber, ProcSpeed, and DisplayType. There are others, but these are the ones that uniquely identify a hotswap unit within our pool.
    I have been trying to figure out the best way to model this part of the database to reflect the following:
    - Model is constrained by Make;
    - ModelNumber is constrained by Model (...and Make, for that matter -- especially if two different manufacturers happen to decide to give their products the same name);
    - There are only so many ProcSpeed and DisplayTypes available, and these have been setup as lookup tables, but they do play a part in uniquely identifying particular hotswap units (i.e. we may have a Toshiba Tecra 8200 1GHz SXGA and a Toshiba Tecra 8200 1GHz XGA -- these need to be separate records, and are inventoried separately)

    I'm pretty new to this, so I'm not sure if this is something I should be able to build into the ER structure, or whether queries will be necessary to perform the actual constraining.
    I have the feeling that the answer is right in front of my face, but I've been going around in circles on this for awhile now.
    Attached Thumbnails Attached Thumbnails hotswaperd.gif  

  2. #2
    Join Date
    Sep 2002

    Re: newbie ERD dillema

    You seem to be along the right lines here. A couple of observations:

    1. You don't need the FK between Make and ModelNum, as it is "inherited" via Model (Model PK is Make,Model, so the FK from ModelNum to Model must be (Make,Model)).

    2. The FK between ModelNum and InventoryUnit should be 1:many also, shouldn't it?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts