How to check field value against same field on existing nodes of same content type I wonder if it possible to check the value of a filed against same field in already existing nodes of same content type.

My case: I have a content type property where people advertise their properties, inside property content type I have a field Phone number. I would like to have a rule to check the value of phone number filed against all the existing properties when user click save on creating new property page and send email to administrator with value of the phone number field.

For my experience the Rules module should be able to do that, but I can't figure how.

How dose Unique field module work?

Knowing about the way Unique field module functionality i can customise the module/create my own to send email if there was a any other content with same phone number
I don't know how to achieve that with rules, but you could use EntityFieldQuery, in a custom submit callback of property_node_form.
Something like that :



/**
 * Implements hook_form_FORM_ID_alter().
 */
function mymodule_form_property_node_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  $form['actions']['submit']['#submit'][] = 'mymodule_property_node_form_submit';
}

function mymodule_property_node_form_submit(&amp;$form, &amp;$form_state) {
  $phone_number = $form_state['values']['field_phone_number'];

  $query = new EntityFieldQuery();
  $query-&gt;entityCondition('entity_type', 'node')
    -&gt;entityCondition('bundle', 'property')
    -&gt;propertyCondition('nid', $form_state['node']-&gt;nid, '&lt;&gt;')
    -&gt;fieldCondition('field_phone_number', 'value', $phone_number)
    -&gt;range(0, 1);

  $same_phone_count = $query-&gt;count()-&gt;execute();

  if($same_phone_count &gt; 0) {
    // send mail
  }
}