SELECT i.item_id FROM items AS i LEFT JOIN mapping AS m ON (m.item_id = i.item_id)
GROUP BY i.item_id HAVING EVERY(m.container_id != 1) OR EVERY(m.container_id != 1) IS NULL

##</code><code>##

my $rs = $schema->resultset('items');
my $items = $rs->search(undef, {
  join => 'mapping',
  group_by => [ map { "me.$_" } $rs->result_source->columns ],
  having => "EVERY(m.container_id != 1) OR EVERY(m.container_id != 1) IS NULL",
});