Re: Partial foreign keys, check constraints and inheritance

Scott Marlowe wrote:

>On Thu, 2005-11-17 at 13:36, Eric E wrote:
>
>
>>Eric E wrote:
>>
>>
>>
>>>>maybe you can solve it adding a new col and allow both to contain
>>>>null values.
>>>>
>>>>if these are not mutually exclusive you can avoid a check if they are
>>>>check that if one has a non-null value other has null...
>>>>
>>>>
>>>I did think about that, but I disliked the idea of two fields of nulls
>>>for every one full field.... maybe it's not as bad a way of doing it
>>>as I thought.
>>>
>>>
>>BTW, in most cases I have 5+ tables to do this, so that's 4+ fields of
>>
>>
>null in each row...Could you use some kind of intermediate join table, so that it pointed
>to orders and then products / customers / othermidlevel tables pointed
>to it, and so did the problems table?
>
Clever - that intermediate table sounds like sort of a GUID for every
element in the database, along with what table it belongs to, and the
problems table points at that GUID.  Sounds pretty promising.  Thanks
for the idea.

EE