Re: Querying join table

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On 5/3/06, Fredrik Liden <flide..ranslate.com> wrote:
> I'm trying to figure out two queries from the following structure.
>
> SURVEY
> SurveyID (PK)
>
> PERSON_SURVEY
> PersonID (PK,FK)
> SurveyID (PK,FK)
>
> PERSON
> PersonID (PK)
>
>
> 1. I have a join table PERSON_SURVEY with a composite key of PersonID
> and SurveyID. How can I query for all the entries where PersonID =
> 'something'. Do I use an expression or a path? Since this is a composite
> key and is part of the PK. In general, is it preferred to stay away from
> composite keys in the join tables?

Yes, I recommend using a composite join table. Cayenne has excellent
support for this situation. Make sure to mark the reverse
DbRelationships as "to dep key". You'll probably need to manually
add ObjRelationships to your Person and Survey ObjEntities.

Once you've configured everything correctly, your join tables will be
invisible to your application. You'll be able to use
person.addToSurveyList() and person.getSurveyList() and
survey.addToPersonList() and survey.getPersonList() transparently.

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