Display category names on edit user profile using $wpdb

Question

The $wpdb->query() method doesn’t return query results but a count on how many rows were affected by the query. To get the results you have to user the $wpdb->get_results($sqlString) method and then iterate over it.

<?php
function custom_user_profile_fields($profileuser) {
?>
<h1>Select a Category</h1>
<select name="category">
  <?php
    global $wpdb;
    $terms = $wpdb->get_results( "SELECT name FROM wp_terms" );
    foreach ( $terms as $term ) { ?>
      <option value=""><?php echo $term->name; ?></option>
    <?php }
  ?>
</select>
<?php
}
add_action('show_user_profile', 'custom_user_profile_fields');
add_action('edit_user_profile', 'custom_user_profile_fields');