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Accessing/displaying 'many to many' data structures

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    Accessing/displaying 'many to many' data structures

    I am used to programming in PHP and Postgres/MySQL and I am struggling to get my head around the way that Alpha Five does things.

    I understand from the documentation that Alpha Five can't display a form or browse for a many-to-many to set, which makes perfect sense, but I don't know how to access/display my data in the way that I want to.

    Firstly, my data.

    As a learning exercise, I am writing a small application that stores the birthdays of friends and family, and sends email(s) just before their birthday, to one or more email addresses.

    So I have two main tables - birthdate and email - and a joining table birthdate_email, because each birthday reminder can be sent to more than one email address, and each email address can be notified of more than one birthday. Birthdate has fields for id, name, birthdate and next birthday, while email has fields for id and email address. Birthdate_email has two fields - birthdate id and email id.

    Secondly, my interface.

    What I have so far is a form with a summary of names and birthdates (as an embedded browse of the birthdates table), from which you can select one record to edit (or add a new one), which opens up a new form, based on one record from the birthdate table.

    What I want to see is, after the person's name and birthdate details, is a set of checkboxes, one for each email address in the email table.

    What I would previously have done, as a conceptual design is:

    1. Queried the email table to return a list/array of all possible email addresses
    2. Displayed all of those email addresses, associated with a checkbox
    3. Queried the birthdate_email table with the current birthdate_id to return a list of email addresses currently set to be notified about this particular birthdate
    4. Marked each of those email addresses as 'checked', and left the remaining email addresses 'unchecked'

    Then when someone checked or unchecked one of those email addresses and saved their changes, this would add or remove records from the birthdate_email table appropriately (or alternatively, mark an extra 'status' field in the birthdate_table against that record as 'inactive' to avoid actually deleting records).

    I just can't get my head around how to achieve this in Alpha Five.

    I realise that my data is fully normalised, and that I could denormalise it a bit which might make it easier (for example, make email_id in birthdate_email a lookup field instead, and possibly get rid of the email table altogether), but this type of data structure is going to come up again and again in the main application I want to build in Alpha Five and I need to crack this nut to feel confident that I can do what I want to in Alpha Five.

    How do I connect my data to my interface to get the desired result?

    Can anyone get me started in the right direction?

    #2
    Re: Accessing/displaying 'many to many' data structures

    Attached is a small example that might give you some ideas
    Tim Kiebert
    Eagle Creek Citrus
    A complex system that does not work is invariably found to have evolved from a simpler system that worked just fine.

    Comment


      #3
      Re: Accessing/displaying 'many to many' data structures

      Thanks, Tim. Much appreciated!

      I'll have a play with your example and see how I go.

      Cheers,

      Nikki

      Comment


        #4
        Re: Accessing/displaying 'many to many' data structures

        OK, so I think I get it now.

        Basically, relationships between tables in Alpha Five are directional. In other words, although one email address may be notified of many birthdays, because you are coming at the information starting from one birthdate, you are effectively filtering your joing table records with that one birthdate_id, which means that there is basically a one-to-one relationship between the filtered joining table records and the email addresses in the email table.

        I think I also now understand sets a bit better. I knew a set design depended on how you wanted to look at the data, and this is a perfect example of that in practice.

        Interesting...

        Thanks again for your help, Tim.

        Comment


          #5
          Re: Accessing/displaying 'many to many' data structures

          I am struggling with this too! Did you ever figure out how to crack this nut, or is the final solution that it just isnt possible in A5

          Comment


            #6
            Re: Accessing/displaying 'many to many' data structures

            Daniel,

            If you are referring to a Many to Many set then this has been covered many times on the messageboard---but is not that easy to find with vBulletin's search I admit.

            Try this link to a search I ran--got a few relevant hits.

            http://msgboard.alphasoftware.com/al...earchid=337083
            Mike
            __________________________________________
            It is only when we forget all our learning that we begin to know.
            It's not what you look at that matters, it's what you see.
            Henry David Thoreau
            __________________________________________



            Comment


              #7
              Re: Accessing/displaying 'many to many' data structures

              Unfortunately, the link Mike offered returns a not found message.

              Comment


                #8
                Re: Accessing/displaying 'many to many' data structures

                Hi,
                Alpha sometimes moves threads--just ran a search and came up with this thread---also check out the similar threads (bottom of each thread) once you find such a thread and it usually points to others.

                http://msgboard.alphasoftware.com/al...ad.php?t=69693
                Mike
                __________________________________________
                It is only when we forget all our learning that we begin to know.
                It's not what you look at that matters, it's what you see.
                Henry David Thoreau
                __________________________________________



                Comment

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