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From Kevin Menard <kmen...@servprise.com>
Subject Re: questions
Date Wed, 13 Feb 2008 18:57:21 GMT
Comments in-line.


On 2/13/08 1:48 PM, "Eric Polino" <aluink@gmail.com> wrote:

> I've started using Cayenne a few weeks ago for our project,
> www.campgroundautomation.com.  In the process of working with it, I've
> come across a few things I don't understand.  After reading the API
> and the UserGuide, can't find much to help me.
> 
> 1.  How do I count the rows of a query, without actually doing a full
> blown SelectQuery and counting the elements?  ie: select count(*) from
> table;

Various aggregate queries come up rather frequently on the list.  I think
someone posted a utility class at one time you could use.  Otherwise,
SQLTemplate will get you there.

http://cayenne.apache.org/doc/sqltemplate-basics.html

> 2.  I've read in many places how Cayenne deals with joins for you, but
> nowhere do I see an example of how its done.  Here's an example
> problem I'm dealing with.
> 
> Schema:
> 
> Reservation (n to 1) Site
> Site (n to 1)
> Site contains a type field
> 
> I want to get all the Reservations of a given for a given type of
> site.  In sql I would execute something like, "select * from
> Reservation, Site, SiteType where SiteType.Name='Something' and
> Site.typeID = SiteType.id and Reservation.siteID = Site.id"
> 
> Short of writing an parameterized sql string and executing that in my
> code, how do I do that with Cayenne?  I hope I explained all that well
> enough...make sense?

Just map the relationships in the modeler.  Cayenne takes care of the SQL
for you.  The following guide should help you get started with the modeler:

http://cayenne.apache.org/doc20/tutorial-starting-mapping-project.html

-- 
Kevin


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