QuizzesReportsGenerator::addQuizActivityFields( $strFields,  $queryArgs )

	public function addQuizActivityFields($strFields, $queryArgs)
	{
		global $wpdb;
		$metaTable = $wpdb->prefix ."learndash_user_activity_meta";
		$table = $wpdb->prefix ."learndash_user_activity";

		$strFields .= ", (
				SELECT mt_points.activity_meta_value
				FROM {$metaTable} as mt_points
				WHERE mt_points.activity_id = ld_user_activity.activity_id
				AND mt_points.activity_meta_key = 'points'
			) as activity_points
		";

		$strFields .= ", (
				SELECT mt_score.activity_meta_value
				FROM {$metaTable} as mt_score
				WHERE mt_score.activity_id = ld_user_activity.activity_id
				AND mt_score.activity_meta_key = 'percentage'
			) as activity_score
		";

		$strFields .= ", (
				SELECT mt_time_spent.activity_meta_value
				FROM {$metaTable} as mt_time_spent
				WHERE mt_time_spent.activity_id = ld_user_activity.activity_id
				AND mt_time_spent.activity_meta_key = 'timespent'
			) as activity_time_spent
		";

		$strFields .= ", (
				SELECT count(*)
				FROM {$table} as mt_attempts
				WHERE mt_attempts.post_id = posts.ID
				AND mt_attempts.user_id = users.ID
			) as activity_attemps
		";

		return $strFields;
	}