clickhouse，数据标记问题

环境：clickhouse

需求：一个会员号，按时间排序，会员等级是连续的咋打上同样的标记

问题遇到的现象和发生背景

用代码块功能插入代码，请勿粘贴截图

直接用窗口函数，标记打上1，2，3这样：

select t.*, rank() over w as flag form test t
WINDOW w AS (partition by department ORDER BY mer_no, date)
SETTINGS allow_experimental_window_functions = 1

窗口函数，多加一列