Re: [SQLObject] Optional One to One Relationships

[David W. <da...@su...>]

Clifford,

>> How would you represent an optional one to one relationship with 
>> SQLObject? A use case would be a system where there is a table for 
>> person and another for donor. A person can be a donor but need not be 
>> a donor. If a person becomes a donor, there must not be more than one 
>> donor row. Donations are handled in another table.
> 
> 
> Answering my own question, one way of dealing with this is to make the 
> foreign key in the dependent table unique. e.g.
> 
> create table donor (
>         id serial primary key,
>         person_id integer unique reference person(id),
>         ...
> 
> Now to figure out how to capture and decode the errors raised by 
> PostgreSQL.

I would use the same primary key as used in the person table as both 
primary key and foreign key. That neatly enforces that you cannot have 2 
donors for one person.

Regards

Dave
--
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