分组后的其他字段去重

count(DISTINCT(product)) num_sold,

分组后数据存放到一个字段 （带着排序，在保存到一个字段）

group_concat(distinct product order by product separator ‘,’)

select sell_date,count(DISTINCT(product)) num_sold,
group_concat(distinct product order  by product  separator ',') 
products from  Activities group by sell_date order by sell_date