Sorting Perl with Class::DBI -

you have following table called pets:

name     age     pet ------------------------ carol     25     null stean     23     cat mel       24     dog rich      24     rabbit 

in mysql database on server mydbserver user of 'user' password of 'password'.

do following:

1) create class::dbi connection database above credentials ( dbi.pm ).

2) create class table pets ( pet.pm )

3) create program prints names of people in pets table , kind (if ) of pet he/she has sorted name age.

here code wrote.....

#!/usr/bin/perl       package pet::dbi; use dbi; use strict; use base 'class::dbi'; pet::dbi->set_db('main','dbi:mysql:dname', 'user', 'password')   or die $dbi::errstr "\n"; 1;  package pet::pets; use base 'pet::dbi'; use strict; use warning; pet::pets->table('pets'); pet::pets->columns(all => qw/name age pet/); 1;  use pet::pets; @pets = pet::pets->retrieve_all;  (sort {$a->name cmp $b->name} || {$a->age <=> $b->age}  @pets) { print "name:".$_->name ' => '."age". $_->age"\n"; }  1; 

it's correct, there's number of small problems.

it's not necessary load dbi, class::dbi take care of you.

you should using connection instead of set_db("main", ...). set_db comes ima::dbi , it's not polite (or necessary) peek under hood that.

although isn't directly documented in class::dbi (it should be), inherited ima::dbi, there's no need check dbi errors. raiseerror on , if connection fails throw error.

you have typo, use warning; instead of use warnings;.

unless have stitched 3 files post, if code in 1 file 1; statements nothing. use pet::pets not work because there no pet/pets.pm file. don't have use class in same file.

in general, avoid using $_ if don't have to, many things can quietly use or change it. instead, give loop proper variable for $person.

sort takes 1 block, you're correct. should sort { ($a->name cmp $b->name) || ($a->age <=> $b->age) } @pets

to avoid reading whole, potentially large, table memory, sorting should done in database order name asc, age asc , retrieved row @ time using iterator. unfortunately, retrieve_all not support options. can use retrieve_from_sql add arbitrary sql end of basic select. my $all_people = pet::pets->retrieve_from_sql("order name asc, age asc"); data sorted , can read row @ time. while( $person = $all_people->next ) { ... }

you're missing . in "age". $_->age"\n".

null values in database come undef. you'll want check if $_->pet defined , if not use other string "no pet" or blank "".

you're printing person's age, question asks pet.

otherwise, should work.

but really, tell whomever gave homework stop telling people use class::dbi. can email me if like, schwern@pobox.com.