Re: Help! Why a relation table takes hard space ?

The referential integrity constraint does not take space on any of your tablespaces. However, when you create an index on a foreign key column in the child table, you will use disk space to store it. This index is separate from the parent table index. The parent table primary key has unique values for each row, but this do not have to be true for the child table.

In your example below, the rows in the R_AB table whill use disk space just as any other table data. For each connection you want to make between tables a and b, you need to store a row in r_ab.

-magnus.

"Maison" <maisonborniol_at_my-deja.com> wrote in message news:dd4cf02c.0202260917.137bd596_at_posting.google.com...
> Hi,
>
> If I have table A with a PK_A primary key and the same with a table B
> and PK_B.
>
>
> I have a relation table between A and B which called R_AB.
>
> R_AB
> -------
> PK_A
> PK_B
>
>
> If I write that PK_A and PK_B are ForeignKey from tables A and B, does
> the R_AB table takes any disk space more ?
>
> The index are already defined in the table A and B.
>
> Why ?
>
>
> Thanks !
Received on Tue Feb 26 2002 - 12:50:46 CST