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One to Many Relationships

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    One to Many Relationships

    If someone could point me in the right direction, I would be grateful. I have spent the past three weeks to solve this, and I am stumped.

    I am doing a database for ordering model cars off the Internet. The database is set up in MYSQL.

    There are two tables each with a primary key.

    Table 1: Car Model
    Modelid Modelname

    Table 2: Car Color
    Colourid Colourname


    One Car Model can have many Car Colours (Red, Blue, Yellow)

    In MYSQL I set up a Third Table called ModelColour where the three fields are:

    Table 3: ModelColour
    Incrementing Primary Key Modelid Colourid


    A car can come in about 15 colours, but there are approximately 75 different colours available.

    I'd like to have all 75 colours done in checkbox form, so the person entering the car information can choose 15 colours at once, rather than entering the same car information in each time, but changing the colour 14 more times.

    In effect, every time a box is checked on the FORM, it would store a separate record and thus, without refreshing the page, Table 3 would look like this:

    Table 3: ModelColour
    Incrementing Primary Key Modelid Colourid
    ------------------------ ------- --------
    1 Model1 111
    2 Model1 112
    3 Model1 113


    My question is, is this possible in my current set up?

    Or should I do a separate table for each of the 75 colours and use a on/off switch for each field?

    Thanks for any help and your patience if this is a much discussed topic that I have overlooked.

    Joel
    Last edited by 13axtula; 04-26-2010, 11:06 PM. Reason: A few grammar mistakes.
    My Alpha Five Site: http://www.whattopair.com

    #2
    Re: One to Many Relationships

    I don't know. Maybe you could have a 1:1 relationship?

    Car Model [1:1] Car Color

    Car Color could have 75 fields.

    But if you need to have only the 15 colors associated w. a model, I would code some kind of copy operation where you copy the relevant colors to Car Color. Something like that.
    Peter
    AlphaBase Solutions, LLC

    [email protected]
    https://www.alphabasesolutions.com


    Comment


      #3
      Re: One to Many Relationships

      You have a very complex problem. What I would do is have a table that contains all of the available colors. I would have a car model table that contains all of the available models. I would have an orders table that contains an orderid that you assign, the modelid, and a text field that is large enough to hold a string with all 15 of the chosen colors like 'red,blue,green,orange,purple,etc,etc' In the orders grid I would have an edit combo list lookup with the modelname from the car model table that fills in the modelid to the orders table.
      Now for the hard part I would have a grid component lookup in the orders grid on the color text field that contains all of the available colors from the colors table. Include a checkbox select column in this grid. The user would open the grid and select 15 of the available colors, you would have to write some code to limit them to 15 choices. Then write the code to extract the first 15 colors selected and create a string to store to the color field. Just a thought.

      orders table would look like;
      modelid, colorstring, orderid
      123, 'red,blue,green,orange,black,white,etc,etc', 1

      or the orders table could have 1 record for each color like;

      modelid, color, orderid
      123, red, 1
      123, green, 1
      123, blue, 1
      123, orange, 1
      123, etc, 1


      may the force be with you....
      Win 10 64 Development, Win 7 64 WAS 11-1, 2, Win 10 64 AA-1,2, MySql, dbForge Studio The Best MySQL GUI Tool IMHO. http://www.devart.com/dbforge/mysql/studio/

      Comment


        #4
        Re: One to Many Relationships

        I think you've got the basic tables correctly done, however I would add a unique id field to CarModels and CarColors as you have for ModelColors. It's not really required if the ModelID and the ColorID's are always unique but I think it's a good idea.

        In my mind, you've described a many to many relationship.
        Each model can come in many colors.
        Each color can be assigned to many models.

        There really is no reason to limit the selection to say 15 colors because the modelColors table drives the selection and you can limit that to whatever you want.

        The missing tables relate to the orders and I would add an order_header table and an order_details table.

        As far as the color selection on per model basis, the simplest method is probably to use a combo/box lookup based on a view that includes the modelID, ColorID and ColorName. Filter by Model ID and show color name, you can return either ColorID, ColorName or both to the order_details table. The only hassle you will have here is duplicate colors but you can force the color to be unique in the order details table on the backend and handle that in one of the Xbasic event handlers.
        Bob Moore


        Comment


          #5
          Re: One to Many Relationships

          Thank-you Peter, Frank, and Bob. Your comments and suggestions are extremely helpful!

          Joel
          My Alpha Five Site: http://www.whattopair.com

          Comment


            #6
            Re: One to Many Relationships

            The architecture would depend on whether or not you needed a stock count of models by color. eg red xtl100's blue xtl100's. If this is the case then you absolutely need to have a unique model for each color.

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