Arthur Fuller
fuller.artful at gmail.com
Thu Apr 10 17:06:39 CDT 2014
Sorry to add an additional layer to this problem, but I need to. Most of the foregoing replies cover the required Inserts and Updates, but neglect the problem that all Inserts, Updates and Deletes by definition destroy the previous data-history. In the trivial example, Employee X may have been promoted to Executive Level Y, and if all you do is change her LevelID from 1 to 2 then you automatically lose her history. This is why I and several others have created and evolved the PITA solution. You can read about it in detail by visiting Red-Gate.com and searching for PTA (they were afraid of the other interpretation of the abbreviation). To reduce the content to a short email message, the point is this: every update or insert or delete destroys the data as it existed yesterday. Given just one or two sample domains, a) over the course of your life, you have had several family physicians, or perhaps several divorce lawyers, or realtors, and so on. On Thu, Apr 10, 2014 at 8:07 AM, Susan Harkins <ssharkins at gmail.com> wrote: > Jon, although a bit tedious, could you share the basic table and key > structures you're currently working with? You don't need to include all > your fields, just the fields included in the relationship. > > Susan H. > > > On Thu, Apr 10, 2014 at 1:54 AM, Bill Benson <bensonforums at gmail.com> > wrote: > > > Here is my understanding, it's late and I may be off base. > > > > Many to many relationships are handled by exploiting the separate many to > > one relationships from the component pieces (call - job and > call-contact), > > using a cross table. > > > > Your jobcontactcall table is a (often misnamed) "lookup table" but more > > accurately termed a cross table. It needs minimally, a fkcontactid field > > (note: what if it was a conference call with 3 company reps?? Might need > > columns for a callcontact1, callcontact2, callcontact3, etc ) as well as > a > > fkjobid field. And what if on the same call you discussed 3 jobs? > > Disgusting stuff... > > > > The contact table has a fkcompanyid field of course. Or you can come at > > company through job as well. > > > > CompanyContacts are a touchy business. > > > > There is the dilemma of storing all contact details even for obsolete > > contact rows, so that details of what happened with whom and where can be > > maintained; yet one doesn't want to assume a contact is still at the > > company either. People move all the time, titles change, etc. > > > > Suppose a transaction was created when someone was a project manager. And > > someone else takes on that role. You have to weigh whether you need to > know > > they were a project manager at the time of a transaction (or at least > > listed as one), versus the need to know what role they are currently > > occupying so as to not call them if they are no longer in that role, yet > > that role must be consulted. > > > > If you just update their role you invalidate the history. > > > > So what you end up with is many contactid values for the same actual > > person, preferably only one active at a time. That or keep detailed logs. > > On Apr 9, 2014 11:59 PM, "Jon Albright" <jon.albright at hawaii.rr.com> > > wrote: > > > > > Hi, I have a bit of a struggle with this concept. It's been several > > years > > > that I have done anything with database applications..not since using > > > Foxpro. Anyway, I work for a contractor and have a need to maintain a > > > customer table (contractor general information), a table for the > contact > > > people at the contractor's companies, a projects table (jobs we bid) > and > > a > > > table to log phone calls. I have the tables created with an > "associate" > > > table for the M2M relationship between the customer table and the jobs > > > table, another "associate" table between the customer contact table and > > the > > > phone calls table. I also have a one to many created between the > > customer > > > table and customer contact table. > > > > > > > > > > > > If I create forms for either of the two M2M examples above, they work > > fine > > > as a standalone but I just can't seem to "tie" the two M2M examples > into > > a > > > functioning arrangement where if you select a company, all the phone > > calls > > > made by the contact people at the company will display and likewise, > if I > > > select a particular job, all the phone calls relating to this job > > display. > > > I have followed an example by Susan Harkins from 2004 that I dug up in > a > > > search but am still unable to get beyond the basic. > > > > > > > > > > > > > > > > > > Jon Albright > > > > > > Iniki Enterprises > > > > > > Honolulu, Hawaii > > > > > > (808) 677-7800 x116 > > > > > > > > > > > > -- > > > AccessD mailing list > > > AccessD at databaseadvisors.com > > > http://databaseadvisors.com/mailman/listinfo/accessd > > > Website: http://www.databaseadvisors.com > > > > > -- > > AccessD mailing list > > AccessD at databaseadvisors.com > > http://databaseadvisors.com/mailman/listinfo/accessd > > Website: http://www.databaseadvisors.com > > > -- > AccessD mailing list > AccessD at databaseadvisors.com > http://databaseadvisors.com/mailman/listinfo/accessd > Website: http://www.databaseadvisors.com > -- Arthur