in reply to Use a hashref as a key in another hashref?

For interest the same task using a database could look like the following:

use strict;
use warnings;
use DBI;

my @date = qw(year month day hour minute);
my @items = qw(burgers fries sodas);
my @fields = (@date, @items);
my @entries      = (
    makeEntry(
        'day'          => 1,
        'month'        => 1,
        'year'         => 2000,
        'hour'         => 4,
        'minute'       => 44,
        'burgers' => 5,
        'fries'   => 3,
        'sodas'   => 11
    ),
    makeEntry(
        'day'          => 1,
        'month'        => 1,
        'year'         => 2000,
        'hour'         => 4,
        'minute'       => 45,
        'burgers' => 2,
        'fries'   => 4,
        'sodas'   => 7
    ),
);

unlink 'delme.sqlite';

my $dbh = DBI->connect("dbi:SQLite:dbname=delme.sqlite","","");
my $sql = <<SQL;
CREATE TABLE Sales (
    year INTEGER,
    month INTEGER,
    day INTEGER,
    hour INTEGER,
    minute INTEGER,
    burgers INTEGER,
    fries INTEGER,
    sodas INTEGER
    )
SQL

$dbh->do ($sql);

my $columns = join ', ', @fields;
my $places = join ', ', ('?') x @fields;
my $sth = $dbh->prepare ("Insert INTO Sales ($columns) VALUES ($places
+)");

$sth->execute(@$_) for @entries;

$sth = $dbh->prepare("select * from Sales order by Year, Month, Day, H
+our, Minute");
$sth->execute();

while (my $row = $sth->fetchrow_hashref()) {
    printf "%04d/%02d/%02d %02d:%02d:00\n", @{$row}{@date};
    printf "   %-7s %s\n", $_, $row->{"${_}"} for @items;
}


sub makeEntry {
    my %row = @_;
    return [@row{@fields}];
}

[download]

Prints:

2000/01/01 04:44:00
   burgers 5
   fries   3
   sodas   11
2000/01/01 04:45:00
   burgers 2
   fries   4
   sodas   7

[download]

But now that you have the data in a database you have much better options for extracting interesting information. For example, you can now order the output by, say, soda sales with a simple change to the select (select * from Sales order by fries desc, Year, Month, Day, Hour, Minute) or look at sales during a particular time each day (select * from Sales Where minute = 45).

Perl is the programming world's equivalent of English

Replies are listed 'Best First'.
Re^2: Use a hashref as a key in another hashref?
by poj (Abbot) on Jun 05, 2014 at 12:20 UTC
    Or 'Relational' like this perhaps 
    #!perl
use strict;    
use warnings;
use DBI;

#create db
my $dbfile = 'database.sqlite';
unlink($dbfile);
my $dbh = DBI->connect('dbi:SQLite:dbname='.$dbfile , undef , undef , 
                {RaiseError =>1, AutoCommit =>0}) or die $DBI::errstr;
$dbh->do('CREATE TABLE STATS (ID    integer,
                              DTIME time, 
                              PRIMARY KEY (ID))');
$dbh->do('CREATE TABLE SALES (ID integer,
                              PRODUCT, 
                              VOLUME integer, 
                              PRIMARY KEY (ID,PRODUCT))');
$dbh->do('CREATE TABLE PRODUCT (PRODUCT, 
                                SECTOR, 
                                PRIMARY KEY (PRODUCT))');
$dbh->commit;

# load data
my $sth = $dbh->prepare('INSERT INTO STATS VALUES (?,?)');
while (<DATA>){
  chomp;
  last if $_ eq 'PRODUCT';
  my ($id,@f) = split ',';
  my $dt = sprintf "%04d-%02d-%02d %02d:%02d:00",@f[2,1,0,3,4];
  $sth->execute($id,$dt) if ($id);
  print "STATS INSERT $id,$dt\n";
}
$dbh->commit;

$sth = $dbh->prepare('INSERT INTO PRODUCT VALUES (?,?)');
while (<DATA>){
  chomp;
  last if $_ eq 'SALES';
  my (@f) = split ',';
  $sth->execute(@f) if (@f==2 );
  print "PRODUCT INSERT @f\n";
}
$dbh->commit;

$sth = $dbh->prepare('INSERT INTO SALES VALUES (?,?,?)');
while (<DATA>){
  chomp;
  my (@f) = split ',';
  $sth->execute(@f) if (@f==3);
  print "SALES INSERT @f\n";
}
$dbh->commit;

# report Sales in Sector By Year
print "\n";

my $sql = "SELECT strftime('%Y',DTIME) as year,SECTOR,SUM(VOLUME) AS t
+otal 
           FROM SALES AS sa
           LEFT JOIN STATS AS st 
              ON sa.ID = st.ID
           LEFT JOIN PRODUCT AS pr 
              ON sa.PRODUCT = pr.PRODUCT   
           GROUP BY year,SECTOR
           ORDER BY total";           

my $ar = $dbh->selectall_arrayref($sql);

print "REPORT\n";
printf "%4s %-10s %6s\n",qw(Year Sector Volume);
printf "---- ---------- ------\n";
for (@$ar){
  printf "%4d %-10s %6d\n",@$_;
}

__DATA__
1,1,1,2000,4,44
2,1,1,2000,4,45
PRODUCT
burgers, food
fries, food
sodas, drink
SALES
1,burgers,5 
1,fries,3
1,sodas,11
2,burgers,2 
2,fries,4
2,sodas,7

    [download]

    Produces

    REPORT
Year Sector     Volume
---- ---------- ------
2000  food          14
2000  drink         18

    [download]
    poj
[reply]
[d/l]
[select]

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