从DZ4.1升级DZ5.0出现这种情况,怎么办?

Discuz! info: MySQL Query Error

Time: 2006-9-3 11:13am
Script: /bbs/upgrade7.php

SQL: ALTER TABLE cdb_announcements ADD redirect tinyint(1) NOT NULL default 0 AFTER subject
Error: Duplicate column name 'redirect'
Errno.: 1060