--- In php_mysql@yahoogroups.com, Pete <[EMAIL PROTECTED]> wrote: > > Your problem is that you have designed your database incorrectly. > > You should have a Dealer table, which is what you already have. > dealerID 1 > dealercompany ABC Motors > dealeraddress... phone... etc > > But then you should have a Makes table. > makeID 5 makename Jaguar > makeID 6 makename Mazda > > Finally, you should have DealerMakes table > DealerMakesDealer 1 DealerMakesMake 5 > DealerMakesDealer 2 DealerMakesMake 5 > DealerMakesDealer 2 DealerMakesMake 6 > > If you make the key for DealerMakes as DealerMakesDealer + > DealerMakesMake, and make it UNIQUE, you will never any duplicates. > > With these tables, you can easily see which Makes each Dealer carries, > and you can also find which Dealers carry which Make > > You are breaking 2 basic rules of design: Never have the same > information more than once (you have Jaguar in your example twice), and > never have one field carrying more than one piece of information (ford, > toyota...). > > This design would not only mean that your current problem could never > arise, but in the future, when Jaguar make CityCars and CountryCars, you > can find and expand your information about Jaguar, because it is all in > one place, in the Makes table, and if you decide to make a Models table, > you know where to attach it. > > And don't say that your databases will never change in the future, I > have been working on databases for years, and still haven't found one > that hasn't changed as situations in the real world change. > > -- > Pete Clark > Thanks Pete. I've already done the type of design you mention before, but a very experienced database programmer (certainly more experienced than I am)suggested using one field with comma separated values, and then to extrapolate the values once returned from a database query. But he won't tell me how he did it. I was guessing it was by using some form of array function, but I'm a total newbie to these.
Just hoped someone could explain how it was done. Thanks again for your response. Richard >
