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Sets - Integrity

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    #1

    Sets - Integrity

    I have a question regarding sets. In the form where you choose to link a parent to a child, there is a combo box for Referential Integrity. Just below that box is one entitled "Include record from parent table". Here you have three choices i.e. 1. "Always-even if no matching child record exists", 2. "Only if a matching child record DOES exist" and 3. "Only if a matching child record does NOT exist".

    My question is to what does this refer? If one creates a simple parent-child set and then adds a record to the parent, no record is created for the child, no matter which of the selections above is made. Therefore, I'm guessing that this selection has nothing to do with the creation of records, only the deletion of records. But then what does the referential integrity do? One would think that that would be the place for deletions of records.

    I'm not sure now if I'm confused or this is some sort of bug.

    Anyone care to help me out?

    Charlie
    Tags: None
    #2
    RE: Sets - Integrity

    This covers the case where there are no matching child records. Sometimes you only want to see parent records that do not have a child record, also most times the parent record is not needed if there are no matching child records. So you can make your choice or have more than 1 set if you need to view special circumstamces.
    efs

    Comment

      #3
      RE: Sets - Integrity

      If you select #2, then parent records without matching child records will not be shown.
      efs

      Comment

        #4
        RE: Sets - Integrity

        Ah.....so.....

        The crystal is becoming clear!

        I understand now. I just never had an application where I needed to view things this way, so I never thought of it. What I do have is an application where I need to ensure that there is a child associated with every parent. I haven't figured out how to force this yet, but I'm working on it.

        Thanks Ed.

        Charlie

        Comment

          #5
          RE: Sets - Integrity

          Steven

          My sense is that this is simply a viewing issue, separate from the referential integrity issue, and that is what causes some confusion since they are placed almost as one...

          If whether to view a parent with or without a child is actually "referential integrity", maybe one of our database experts can say... if not Alpha could put a little separator in :-)

          =======================================================
          Now my understanding of referential integrity has to do with changing or deleting records.. and is handled in the item above...

          E.g.
          If you try to delete or change the parent leaving orphaned non-referential child records, such a change or deletion could be cascaded to the child records .. (there should be warning, too) ...

          Similarly if you tried to add or change a child record away from referential relationship, you would be prevented or warned .... (not sure how it handles change from one parent to another existing parent)

          Now on the main language I have used in the past, we didn't have this built-in, it was code handled.. and it is nice to have it as a language facility..

          =======================================================

          Comment

            #6
            RE: Sets - Integrity

            Hello Steven,

            >>E.g.
            If you try to delete or change the parent leaving orphaned non-referential child records, such a change or deletion could be cascaded to the child records .. (there should be warning, too) ...

            You've pretty much zeroed in on this, but:

            >>Similarly if you tried to add or change a child record away from referential relationship, you would be prevented or warned ....

            Comment

              #7
              RE: Sets - Integrity

              Agreed, well put, the proper way to enforce referential integrity is generally not to allow primary key changes..

              If you need a set to allow change of primary parent and child keys make a special set to only eg "change Invoice#", make sure it is properly secured in terms of who can get at it, give it proper logging/auditing/checking of the change, and within that (almost never used) set, you could turn on referencial integrity...

              I'm not sure exactly what a 13X performance degradation means, since I don't know what a 1X degradation means, but it sounds real mean and something to be avoided... :-)
              ========================================================

              Comment

                #8
                RE: Sets - Integrity

                Steven,

                If I recall correctly, referential integrity imposes another performance penalty that can be very troublesome in a networked multi-user setting. When a change begins in the parent record using a set based form, referential integrity requires Alpha to lock all the related records in all the child tables of the set, so that it can cascade changes or deletes. This increases substantially the potential for conflict with work other users may be doing at the time.

                -- tom

                Comment

                  #9
                  RE: Sets - Integrity

                  Hi Tom,

                  You wrote, "This increases substantially the potential for conflict with work other users may be doing at the time."

                  I think it may do this but it is not inevitable and depends on the nature of the application.

                  I know that invoice numbers are very unlikely to change but I'll use the invoice example because it is easy. With referential integrity enabled the line items linked to the invoice header will be locked (which takes resources) but is it realistic to assume that a second user would want to open those line items outside of the context of the set? I can only think of doing so for purposes of counting inventory but wouldn't line items typically be posted to a separate inventory table?

                  So I don't see the problem. Certainly there is no problem with Referential Integrity in my biggest networked application. And it is there for a real reason so it is necessary.

                  Bill
                  Bill Hanigsberg

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