[Dbix-class] RE: SQL Generation with SQL::DB

[Mark Lawrence]

On Tue Sep 11, 2007 at 02:40:03PM +0200, Emanuele Zeppieri wrote:

> Supposing you get the usual hash at runtime:
> 
> my $form = {
>     name   => '= Mark',
>     age    => '<= 30' ,
>     height => '> 180' ,
>     weight => '< 80'
> };
> 
> with SQL::DB (*and* string manipulations) the code would simply be:
> 
> my @predicates;
> while ( my ($field, $expr) = each %{ $form } ) {
>     push @predicates, '($table->' . "$field $expr)"
> }
> 
> # It's a string!
> my $full_expr_str = join ' & ', @predicates;
> 
> And then you can simply do:
> 
> my $expr;
> eval '$expr = ' . $full_expr_str;
> 
> print $sql_db_schema->query(
>     select => [ $table->person_id ],
>     from   => [ $table ],
>     where  => $expr
> );
> 
> It works since 'eval $string' is executed in the lexical context of the 
> calling program (I even forgot that, which makes things even easier :-)
> 
> I realized that SQL::DB was not conceived for that, but why shouldn't 
> the above code work?

Looks perfectly valid to me, with the usual proviso's associated with
parsing / interpolating strings.

> Well, that's one of the situations I meant where SQL::DB could be useful 
> (even more in the example in point 4), *provided* that you resort to 
> string concatenations.
> 
> Please, let me know if I've finally been able to be clear.

Yep. Fully up to speed now.

-- 
Mark Lawrence