如果你想删除UserName元素，那么你可以在XMLQUERY语句中使用FLOWR表达式来更新表中的所有现有值：

UPDATE login
SET value = XMLSERIALIZE(
              CONTENT XMLQUERY(
                'copy $e := /login
                 modify (
                   for $i in $e/UserName
                     return delete node $i
                 )
                 return $e'
                PASSING XMLTYPE(value)
                RETURNING CONTENT
              )
              AS CLOB  
            );

字符串
如果你想修改所有被INSERT艾德化的值，那么使用一个触发器：

CREATE TRIGGER remove_username
BEFORE INSERT ON login
FOR EACH ROW
BEGIN 
  SELECT XMLSERIALIZE(
           CONTENT XMLQUERY(
             'copy $e := /login
              modify (
                for $i in $e/UserName
                  return delete node $i
              )
              return $e'
             PASSING XMLTYPE(:NEW.value)
             RETURNING CONTENT
           )
           AS CLOB  
         )
  INTO   :NEW.value
  FROM   DUAL;
END;
/

型
fiddle