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From "Gentry, Michael \(Contractor\)" <michael_gen...@fanniemae.com>
Subject RE: Query Examples Needed � Expression.fromString() syntax?
Date Wed, 24 May 2006 20:44:53 GMT
I don't know which is more efficient as I've never timed them.  I'd be willing to wager that
your database latency will be significantly higher than having to choose between Expression
and ExpressionFactory, though.  Perhaps a case of trying to optimize too early?

I just prefer the way fromString() works so that is what I use.  It fits my brain better.
 I believe fromString() appeared in Cayenne 1.1, so before that you had to do it the other
way (unless I'm just totally off here).

Use whichever one feels better to you.  :-)

/dev/mrg


-----Original Message-----
From: Eric Lazarus [mailto:ericllazarus@yahoo.com] 
Sent: Wednesday, May 24, 2006 3:45 PM
To: cayenne-user@incubator.apache.org
Subject: Re: Query Examples Needed � Expression.fromString() syntax?


Thank you, Michael and Joshua! 

What about efficiency? If I want to "and" in a bunch
of things, like as many as 10 things if the user fills
in all the fields of the web query form, then it would
look like this? :

Expression e =
ExpressionFactory.greaterExp("estimatedPrice", new
BigDecimal(100000.0));

e = e.and( ExpressionFactory.lessExp("estimatedPrice",
new
BigDecimal(5000.0)) );

e = e.and( ExpressionFactory.lessExp("productSize",
BigDecimal(100.0) );

e = e.and( ExpressionFactory.lessExp("productWeight",
new
BigDecimal(200.0)) );

I can just keep appending conditions on like this?
Will this turn into efficient SQL code if done this
way? If not, what is the best way?

Thanks,

Eric

--- Joshua Pyle <joshua.t.pyle@gmail.com> wrote:

> I never use fromString any more.
> 
> But using the expressionFactory to and and or
> expressions is very simple...
> 
> Expression e =
> ExpressionFactory.greaterExp("estimatedPrice", new
> BigDecimal(100000.0));
> 
> e = e.and(
> ExpressionFactory.lessExp("estimatedPrice", new
> BigDecimal(5000.0)) );
> 
> -- 
> Joshua T. Pyle
> Go has always existed.
> 
> On 5/24/06, Eric Lazarus <ericllazarus@yahoo.com>
> wrote:
> > Would anyone reply with some nice examples of
> > SelectQuery beside the simple one here:
> >
> >
>
http://www.objectstyle.org/cayenne/userguide/dataobjects/dataobjects-example.html
> >
> > Expression e =
> >   ExpressionFactory.greaterExp("estimatedPrice",
> >                         new BigDecimal(100000.0))
> >
> > I need to do things with ANDS and ORs and I'm not
> sure
> > how to use expression factory (or should I use
> > Expression.fromString() ?) to do it.
> >
> > Right now my immediate need is to be able to
> construct
> > a query with an arbitary number of possible "and"
> > clauses depending on what the user types.
> >
> > Seems like fromString() is going to be easy and
> > powerful but I can't find an example of the syntax
> > using google.
> >
> > Even just a few nice examples would be helpful.
> >
> > Can I look at the attributes of sub objects using
> this
> > syntax? How?
> >
> > Thanks!
> >
> > Eric
> >
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Tired of spam?  Yahoo! Mail has the best spam
> protection around
> > http://mail.yahoo.com
> >
> 
> 
> -- 
> Joshua T. Pyle
> Go has always existed.
> 


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