Conditional statement if an entries relation field is empty?

gistfile1.txt

{% if entry.fieldHandle |length  %}
  {{ entry.fieldHandle}}
{% else %}
  {{ global.fieldHandle}}
{% endif %}


How can I conditionally display content if its a specific section?

{% if entry.section.handle == 'lettings' %}
    {{ entry.rentFrequency.label }}
{% endif %}

Conditional dependent on the length of a field within a matrix field:
{% if block.destination | length > 25 %}<br />{% endif %} {{ block.smallCost }}