Error: You have an error in your SQL syntax; check the manual that corresponds t

[51/54]升级表 brand_xml_client 出错,请手工执行以下升级语句后,再重新运行本升级程序:

升级SQL语句: ALTER TABLE brand_xml_client CHANGE `clientid` `clientid` varchar(50) NOT NULL, DROP INDEX `varchar(50)`, ADD INDEX `varchar(50)` NOT NULL

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NOT NULL' at line 1
Errno.: 1064