class design vs. db design

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John_Woo - 19 Dec 2006 12:32 GMT

Hi,

if I want to reflect a 1:1 relationship for user:account, the design
model may be:

for class:
A. User
-------------
int user_id;
int account_id;

B. User
------------
int user_id;
Account account;

for db:
C. User (user_id int); Account(account_id int, user_id int)

D. User (user_id int, account_id int); Account (account_id int)

Questions:
1. How to compare A vs. B in terms of OO design, JDO (java data object)

2. How to compare A vs. B in terms of db schema (with foreign key
constraint)

3. C vs. D, which is better? should create user first or account first?

---
Thanks
John
Toronto

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Oliver Wong - 19 Dec 2006 18:46 GMT

> Hi,
>
[quoted text clipped - 19 lines]
> Questions:
> 1. How to compare A vs. B in terms of OO design, JDO (java data object)

I like B better. It looks like less work to get the account from the
user.

> 2. How to compare A vs. B in terms of db schema (with foreign key
> constraint)

I suppose A would be slightly less work to implement a ORM for, but you
could just download an ORM like Hibernate to do the work for you, so I'd
still stick with B.

> 3. C vs. D, which is better? should create user first or account first?

If the relation is 1:1, why not stick it all in one big table?

- Oliver

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John_Woo - 19 Dec 2006 20:27 GMT

> > for db:
> > C. User (user_id int); Account(account_id int, user_id int)
[quoted text clipped - 4 lines]
>
> If the relation is 1:1, why not stick it all in one big table?

Good point, thanks, Oliver.

but both these two tables may extend, like USER may have 10+ fields,
same as Account table.
if they have to be separated, I'm still looking for tips on selection
of model C, D

John

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class design vs. db design

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