Обсуждение: Unique key field or serverl fks ?

Hi,

I would like to know opinions about which approach is better:

Having a table with a field that works as a unique key, or having 
several fks that work as a combined key ( all the fks fields )?

Thanks in advance,

K.

On Monday 12 January 2004 05:51, katarn wrote:
> Hi,
>
> I would like to know opinions about which approach is better:
>
> Having a table with a field that works as a unique key, or having
> several fks that work as a combined key ( all the fks fields )?

Depends on the particular situation, you'll need to give details of the tables 
and their place in your system.

There are two reasons I've seen given for using an artificial (substitute) 
primary key:
1. It's "lighter" than several other fields (especially where they are text)
2. The natural primary key has meaning to the users, and the users will tend 
to get it wrong.

The second is probably the more persuasive - the first can definitely have 
costs as well as benefits.

--  Richard Huxton Archonet Ltd

>>Hi,
>>
>>I would like to know opinions about which approach is better:
>>
>>Having a table with a field that works as a unique key, or having
>>several fks that work as a combined key ( all the fks fields )?
>>    
>>
>
>Depends on the particular situation, you'll need to give details of the tables 
>and their place in your system.
>
>There are two reasons I've seen given for using an artificial (substitute) 
>primary key:
>1. It's "lighter" than several other fields (especially where they are text)
>2. The natural primary key has meaning to the users, and the users will tend 
>to get it wrong.
>
>The second is probably the more persuasive - the first can definitely have 
>costs as well as benefits.
>
>  
>
Ok, thanks for answering, example:
   Articles Table       articleid   Warehouses Table       warehouseid   Locations per warehouse Table
warehouseid(fk)       locationid       description   Articles Per warehouse       warehouseid (fk)       articleid (fk)
     locationid (fk)       stock
 

In the Articles per warehouse the "primary key" is  the cominbation of 3 
fks. Is that kind of situation acceptable or it could be better to have 
a unique primary key field in addition to the fks? This "gets worse" if 
another table has information binded to the articles per warehouse, it 
has to reference the 3 fks in addition to its own key fields.

Thanks in advance,

K.