Athanasius's solution is the traditional perl solution for the problem you presented. In other words put the data in a hash (to organize the pivot) and then post process the output.

If you are trying to leverage some of the databases functionality as you indicated in your second post then you may want to consider $hash_ref = $sth->fetchall_hashref(); rather than the database sort.

If the goal is to use chapter 4 of Dominus's book to minimize memory overhead then you really just have a recursive problem where you need to identify your base state. (a change of date) You might find the following useful in that case. The data must be pre-sorted by date for this to work. Width formatting is not possible in this output since the data will be printed prior to a test of all rows. That shouldn't be a problem for your suggested goal of web output.

#! perl
use Modern::Perl;
my $data;
#load the data
my $last_date ;
while (<DATA>){
    my ($date, $type, $word) = split(/\s+\|\s+/, $_);
    chomp $word;
    # Check for a new date - base state
    if( $last_date and $date ne $last_date ){
        print_out( $last_date, $data );
        $data = {};
    }
    if( exists $data->{$type} ){
        $data->{$type} .= ', ' . $word;
    }else{
        $data->{$type} = $word;
    }
    $last_date = $date;
}
# Pick up the last line
print_out( $last_date, $data );

sub print_out{
    my ( $date, $data ) = @_;
    print $date . ' | ' . ($data->{woody} // '') . 
        ' | ' . ($data->{tinny} // '') . "\n";
}

__DATA__
28 Sep (Fri) | woody | caribou
28 Sep (Fri) | tinny | litterbin
29 Sep (Sat) | woody | wasp
29 Sep (Sat) | woody | yowling
29 Sep (Sat) | woody | gorn
30 Sep (Sun) | woody | intercourse
30 Sep (Sun) | woody | bound
30 Sep (Sun) | woody | pert
30 Sep (Sun) | tinny | newspaper
01 Oct (Mon) | woody | ocelot
01 Oct (Mon) | woody | concubine
01 Oct (Mon) | tinny | antelope
02 Oct (Tue) | woody | vole
02 Oct (Tue) | woody | sausage
03 Oct (Wed) | tinny | recidivist
03 Oct (Wed) | tinny | tit

[download]

Produces this output

28 Sep (Fri) | caribou | litterbin
29 Sep (Sat) | wasp, yowling, gorn | 
30 Sep (Sun) | intercourse, bound, pert | newspaper
01 Oct (Mon) | ocelot, concubine | antelope
02 Oct (Tue) | vole, sausage | 
03 Oct (Wed) |  | recidivist, tit

[download]

TIMTOWTDI!

Update1: changed for to while to honor the iterator concept

Update2: I just noticed I didn't pick up the last line (no base state test when the query ends. (fixed))

Update3: fetchrow_hashref is a better fit and can be used with sort

In reply to Re^3: Pivoting parts of a database table into an HTML table by jandrew
in thread Pivoting parts of a database table into an HTML table by Anonymous Monk

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