over()函数的排序函数有以下几种：
over(order by column_name): 按指定列(column_name)进行升序排序。over(order by column_name desc): 按指定列(column_name)进行降序排序。over(order by column_name1, column_name2): 先按列column_name1排序，若列column_name1相同则按照列column_name2进行排序。over(partition by column_name order by column_name): 按指定列(column_name)进行分组排序。over(partition by column_name order by column_name desc): 按指定列(column_name)进行分组降序排序。over(partition by column_name order by column_name1, column_name2): 按指定列(column_name1)进行分组排序，若列column_name1相同则按照列column_name2进行排序。
