Re: Efficiently finding elements with 0 has_many elements?

[prev] [thread] [next] [Date index for 2005/04/22]

On Fri, Apr 22, 2005 at 10:57:19AM -0400, David Glasser wrote:
> On 4/22/05, Michael Peters <mpeters@xxxxxxxxx.xxx> wrote:
> > dglasser@xxxxx.xxx wrote:
> > One of the nicest things about C::D is that when you try to do something
> > that isn't necessarily built-in or efficient to do in Perl, you can
> > always have the database do it.
> > 
> > Something like this should work for you (depending on how you've named
> > your columns):
> > 
> > __PACKAGE__->add_constructor(
> >     retrieve_all_no_data => 'item.data IS NULL'
> > );
> 
> Hmm. So I bet it'll still be something along the lines of that, but
> the issue is that my Item doesn't have a data column -- it's a
> has_many, and the Data have item columns.  Can something like this
> still work?

Indeed it can - you'll just need to use a JOIN.

Have a look at http://wiki.class-dbi.com/index.cgi?UsingJoins for more info.

        -- 
            Matt S Trout            Brag sheet:    http://trout.me.uk/services.html
LAMP, Infrastructure        Contact:       services@xxxxx.xx.xx
   and Automation
     specialist                                       Do it once. Do it right.