From: Alan Chen <alan@...>
Date: 2002-04-19T02:26:08+09:00
Subject: Re: ruby/postgres problem

On Fri, Apr 19, 2002 at 12:53:52AM +0900, Daniel P. Zepeda wrote:
> 
> On Fri, 19 Apr 2002 00:27:07 +0900
> "Steve Cranford" <stevecranford@cox.net> wrote:
> 
> > I'm trying to determine if a resultset is empty.  if it is, I want to
> > perform other actions.  I tried this code and it didn't work:
> > 
> > result=conn.exec(sql)
> > msg="testing"
> > 
> > if result.num_tuples==0
> >     # run an insert
> >     msg="new action"
> > end
> > 
> > msg<< result.num_tuples.to_s #or a variation, I see the number.
> > 
> > the number of tuples correctly reports on the screen but the if block
> > never executes.  I've had similar problems with numeric values in a case
> > statement.  I've tried using variables in place of the values in the if
> > statement as well as a (!result), but nothing seems to work.  what am I
> > doing wrong?
> > 
> Try more whitespace in the predicate:
> 
> if result.num_tuples == 0 then 
> 
> I know it is not supposed to matter, and I may be mistaken, but I've got
> the impression from experience that sometimes the whitespace does matter. 

Unless you need the column headers, I usually use the conn.query call
which just returns an array of tuples which can be checked with the
regular array call result.size

-- 
Alan Chen
Digikata LLC
http://digikata.com