Source

File: wp-admin/includes/deprecated.php

public function query() {
		global $wpdb;

		$this->results = $wpdb->get_col("SELECT DISTINCT($wpdb->users.ID)" . $this->query_from . $this->query_where . $this->query_orderby . $this->query_limit);

		if ( $this->results )
			$this->total_users_for_query = $wpdb->get_var("SELECT COUNT(DISTINCT($wpdb->users.ID))" . $this->query_from . $this->query_where); // No limit.
		else
			$this->search_errors = new WP_Error('no_matching_users_found', __('No users found.'));
	}