First, your structure makes no sense. I think you mean

@items = ( { item_key         => '1',
             item_description => 'description 1',
             item_summary     => 'item summary 1',
             actions          => [ { key => '1',
                                     summary => 'summary 1'
                                   },
                                   { key => '2',
                                     summary => 'summary 2'
                                   }
                                 ]
           },
           ...
         );
[download]

• You could do multiple queries.

  my $items_sth   = $dbh->prepare('SELECT * FROM Items');
  my $actions_sth = $dbh->prepare('SELECT * FROM Actions WHERE item_key 
  += ?');
  
  my @items;
  $items_sth->execute($item_row->{item_key});
  while (my $item_row = $items_sth->fetch_hashref()) {
     my $item = {
        item_key         => $item_row->{item_key},
        item_description => $item_row->{item_description},
        item_summary     => $item_row->{item_summary},
        actions          => [],
     };
  
     my $actions = $item->{actions};
     $actions_sth->execute($item_row->{item_key});
     while (my $action_row = $actions_sth->fetch_hashref()) {
        push @$actions, {
           key     => $action_row->{action_key},
           summary => $action_row->{action_summary},
        };
     }
  
     push @items, $item;
  }
  [download]

• You could order your query results by item_key and look at the last record key processed

  my @items;
  my $last_key;
  while ($row = $sth->fetch_hashref()) {
     if (!@items || $last_key != $row->{item_key}) {
        push @items, {
           item_key         => $row->{item_key},
           item_description => $row->{item_description},
           item_summary     => $row->{item_summary},
           actions          => [],
        };
  
        $last_key = $row->{item_key};
     }
  
     push @{ $results[-1]{action} }, {
        key     => $row->{action_key},
        summary => $row->{action_summary},
     };
  }
  [download]

• You could use a lookup table

  my %items;
  my @items;
  while ($row = $sth->fetch_hashref()) {
     our $item; local *item = \( $items{ $row->{item_key} } );
     if (!$item) {
        $item = {
           item_key         => $row->{item_key},
           item_description => $row->{item_description},
           item_summary     => $row->{item_summary},
           actions          => [],
        };
        push @items, $item;
     }
  
     push @{ $item->{action} }, {
        key     => $row->{action_key},
        summary => $row->{action_summary},
     };
  }
  [download]

  This method requires more memory. Use the second method if ordering by item_key is acceptable.

You could technically use the last two techniques to build the data structure you desire from the data structure you presented, if you can't build the data structure you desire directly from the database (as shown).

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.