Addresses should definitely have their own table.
Have you considered using Postgres? It allows for table inheritance in
much the same way that inheritance works in OOP. You could have a parent
table (like a parent class) for "People", and child tables (just like
child classes) for "Employee", "non-Customer", and "Customer". This is
the preferred approach, but few other RDMBS solutions support this (or
much SQL 99 at all).
If you're not using Postgres, another way to do this would be to create
a many-to-many relationship between your "People" tables, so that an
address ID is related to a person ID.
Visio balks at using a non-unique foreign key because this is bad
design. A "key" must be unique by nature, and indexing is much faster
the column is guaranteed to have unique values. If you go with your
original approach, make a combined key on both the type and foreign key
fields.
Hope this helps,
Jeremy
Tony Yau wrote:
> Hi Tony, Miguel
>
> yes that was my intention at first, but to absorb all three, Shop,
> Employee, and Customer (and there may be 2 more to come) into an Address
> table would be inefficient both in storage space and search time,..no?
>
> having this compound keys at a separate Address table is essentially the
> same idea, but I know it doesn't 'feel' right, for a start in Visio I can't
> put a link to the Address table (because fkey can't be a foreign key to both
> Shop and Employee)!!!
>
> Apart from that, the tables are efficient, searching would be much quicker
> for non-address info.
>
> Tony
>
> "Tony S. Wu" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
>
>>actually, no, Shop, Employee, and Customer are not distinct.
>>in your instance they are the same type of entry.
>>don't distinguish them by tables, rather use a column to hold some sort
>>of an ID for each type.
>>of course you'll end up with a table with many columns, and many of
>>them will be null depending on which type an entry is.
>>but with this approach, you can easily associate with an address table.
>>
>>Tony S. Wu
>>[EMAIL PROTECTED]
>>
>>
>>
>>On May 14, 2005, at 4:49 AM, tony yau wrote:
>>
>>
>>>Hi Miguel,
>>> Thanks for the reply.
>>>
>>> the non-customer is actually a Shop, so Employee, Customer and
>>>Shop are
>>>distinct enough to have their own tables. Now they all have an
>>>Address, and
>>>the problem is how do I allow multiple addresses for each these
>>>'people'
>>>(without using
>>>a lookup table)
>>>
>>>tony.
>>>
>>>"Miguel Guirao" <[EMAIL PROTECTED]> wrote in message
>>>news:[EMAIL PROTECTED]
>>>
>>>>The schema of your table is wrong, is you do bnormalize it you will
>>>>find
>>>
>>>out
>>>
>>>>that you need two tables for this approach.
>>>>
>>>>One table for your people and another one for the n addresses of your
>>>>people.
>>>>
>>>>If you keep your current schema, you will have as many rows for one
>>>>person
>>>>as many addresses for that person you have, and you will be
>>>>duplicating
>>>
>>>many
>>>
>>>>fields. So you must split your tables, one for your people and
>>>>another for
>>>>your people's addresses.
>>>>
>>>>-----Original Message-----
>>>>From: tony yau [mailto:[EMAIL PROTECTED]
>>>>Sent: Viernes, 13 de Mayo de 2005 09:27 a.m.
>>>>To: php-db@lists.php.net
>>>>Subject: [PHP-DB] novice on table design
>>>>
>>>>
>>>>
>>>>Hi all,
>>>>
>>>>I have the following tables
>>>>
>>>> Employee Customer non-Customer
>>>
>>>Address
>>>
>>>>========== ========== ============= ==========
>>>> pkey pkey pkey
>>>>pkey
>>>> number type type
>>>>...
>>>> payrate grant capital
>>>>
>>>>I need to allow the three types of people to have n addresses, so I've
>>>
>>>added
>>>
>>>>a type to distinguish the 3 types of people and their respective pkey
>>>>onto
>>>>address table.
>>>>
>>>> Address
>>>>=========
>>>> pkey
>>>> ...
>>>> type (either Employee, Customer or non-Customer etc)
>>>> fkey (the pkey of Employee, Customer or non-Customer etc)
>>>>
>>>>I know this design looks awkward but it does have the advantage of
>>>>having
>>>>less tables otherwise.
>>>>BUT somehow it doesn't feel right. Can someone points me its pros and
>>>
>>>cons.
>>>
>>>>thanks all.
>>>>Tony Yau
>>>>
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>>>>PHP Database Mailing List (http://www.php.net/)
>>>>To unsubscribe, visit: http://www.php.net/unsub.php
>>>
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>>>PHP Database Mailing List (http://www.php.net/)
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>>
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