xnau on "[Plugin: Participants Database] Dropdown values from specific field"

Sure, OK. You don't explain if the people who offer the help will type in the name of their activity, or if they choose it from a list. If you let them type it in, you may end up with several slightly different activities that are actually the same activity...this could be confusing to your second group of users. I mention this so you can think about how that might work.

The solution is the same either way.

You can use code something like this to produce your dropdown:

<?php
global $wpdb;
$field = 'activity_title';
$activities = array();
// grab the unique stored values from the field
$result = $wpdb->get_results('SELECT DISTINCT p.' . $field . ' from ' . Participants_Db::$participants_table . ' p WHERE p.' . $field . ' <> ""', ARRAY_N);
// now we convert the query result into a simple array
foreach($result as $value) {
  $activities[] = current($value);
}
// print the dropdown
echo PDb_FormElement::get_element(array(
    'name' => 'selected_activity',
    'type' => 'dropdown',
    'options' => $activities
        )
    );
?>

The database query gets all unique values stored in the 'activity_title' field, then makes a dropdown selector with the values.