安装时发生下列错误，怎么处理：

:)

导入SQL失败，请检查install.sql的语句是否正确:ALTER TABLE `qb_memberdata` ADD INDEX ( `unionid` ) COMMENT '' think\exception\PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 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 'COMMENT ''' at line 1 in /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/db/Connection.php:456 Stack trace: #0 [internal function]: think\db\Connection->execute('ALTER TABLE `q...') #1 /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/Db.php(178): call_user_func_array(Array, Array) #2 /home/beeeefb5e5esele/wwwroot/application/install/controller/Error.php(169): think\Db::__callStatic('execute', Array) #3 /home/beeeefb5e5esele/wwwroot/application/install/controller/Error.php(32): app\install\controller\Error->step5() #4 [internal function]: app\install\controller\Error->index('5') #5 /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/App.php(348): ReflectionMethod->invokeArgs(Object(app\install\controller\Error), Array) #6 /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/App.php(612): think\App::invokeMethod(Array, Array) #7 /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/App.php(461): think\App::module(Array, Array, true) #8 /home/beeeefb5e5esele/wwwroot/thinkphp/library/think/App.php(139): think\App::exec(Array, Array) #9 /home/beeeefb5e5esele/wwwroot/thinkphp/start.php(19): think\App::run() #10 /home/beeeefb5e5esele/wwwroot/index.php(29): require('/home/beeeefb5e...') #11 {main}

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环境检查没有任何问题。