On Jan 29, 2008, at 10:49 AM, MZ_TRICSTA wrote:
One last question, guys. What if there is overlapping between the
child
tables, so that one instance has more than one "Type"?
Then you might want to model this as an Entity-Role relationship which
allows multiple rows in associated tables
On Wednesday 30 January 2008 05:28:14 Craig L Russell wrote:
> The alternative is to include all possible tables in a query, which is
> performance-limiting.
Another alternative is to use single table inheritance, where you still have a
type column but also put every field from every class into t
One last question, guys. What if there is overlapping between the child
tables, so that one instance has more than one "Type"?
Craig L Russell wrote:
>
> This is a very common pattern in object-relational mapping. The column
> that contains the type of crane is commonly referred to as a
> d
Thanks, Craig. Glad to know that this is common practice. I am in the process
of implementing the solution as we speak.
Craig L Russell wrote:
>
> This is a very common pattern in object-relational mapping. The column
> that contains the type of crane is commonly referred to as a
> discrimi
This is a very common pattern in object-relational mapping. The column
that contains the type of crane is commonly referred to as a
discriminator column, and is commonly a CHAR, VARCHAR, or NUMERIC
type. The value of the discriminator column that identifies which
table to look for is referr
Oh! I see. So I would need to add a "Type" column for all my parent tables.
That would definitely make things easier, but I was hoping there was some
SQL code that would magically give me the name of the child table. Still,
this will work fine. Thanks for all your help. ~Tricsta
Brad Moore wrote
2008 10:04:26 -0800
> From: [EMAIL PROTECTED]
> To: derby-user@db.apache.org
> Subject: RE: Determine which child table a record belongs to
>
>
> Thanks for your help, Brad. You are absolutely right. In this case, it
> doesn't make sense to have so many tables. I will
Thanks for your help, Brad. You are absolutely right. In this case, it
doesn't make sense to have so many tables. I will make the changes you
suggest. However, there are times when it does make sense to have this kind
of hierarchical structure such as when the child tables have different
fields, s
Can I suggest changing the "Crane" table to include a CraneType column or
something similar? I don't know if there is a reason that's not obvious to me
why you need all of the other tables. It looks like you're using the other
tables to determine the type of crane, the same thing could be done
