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【DM版本】: DM8.6
【操作系统】：
【CPU】:
【问题描述】*：驱动DmJdbcDriver18-8.1.2.174.jar
达梦数据库执行以下sql，提示Caused by: dm.jdbc.driver.DMException: 存在非法编码字符串，如图

SELECT a.id, a.Id as uid, a.id as user_id,a.user_name,a.email,a.mobile,a.password,a.slug as user_slug,a.photo,a.order_num,a.password_changeable,
a.email_chk,a.mobile_chk,a.status,a.quota,a.used,a.from_domain_account,a.ctime as ctime$,a.mtime as mtime$,a.valid_enable,a.valid_start_time,a.valid_end_time,
b.account_id,b.role from iris_v40.iris_user a ,iris_v40.iris_account_user b where a.id=b.uid and b.account_id = 1
and b.role & 1 >0 and a.status IN(-1,1,0) ORDER BY a.order_num ASC nulls last, nlssort( a.user_name,'NLS_SORT=SCHINESE_PINYIN_M') LIMIT 0, 50

上面的sql去掉 nlssort( a.user_name,'NLS_SORT=SCHINESE_PINYIN_M')可以执行成功，这是为什么，请问如何解决呢？