Re: primary key in a hierarchy

Christophe Geraud wrote:
> Hi,
>
> I have a hierarchy : one element of a table A has a relationship with
> 1..n elements of a table B, and one element of the table B has in
> relationship with one and only one element of the table A.
>
> The table A has a primary key named : ID_A (from a sequence)
> I know two ways to create the primary key for the table B :
> 1. ID_B (independant of ID_A)
> 2. (ID_A, Number)
>
> Is one of the two ways better ?

Not really IMHO, but I would prefer the first one for two reasons:

1. You are not introducing an extra column that has no meaning for the user. (If the column 'Number' was already there then I would take the second solution.)
2. Foreign key references to B will consist of just one attribute.

-- 
  Jan Hidders