All DBs, simple solution
Oracle\n\nselect to_char(a.sell_date, \'yyyy-mm-dd\') sell_date\n    , count(a.product) num_sold\n    , listagg(a.product, \',\') within group(order by a.produc
Oracle\n```\nselect to_char(a.sell_date, \'yyyy-mm-dd\') sell_date\n    , count(a.product) num_sold\n    , listagg(a.product, \',\') within group(order by a.product) products\nfrom (select distinct * from activities) a\ngroup by a.sell_date\norder by a.sell_date\n```\nMy SQL\n```\nselect sell_date\n\t, count(distinct product) num_sold\n\t, group_concat(distinct product order by product asc separator \',\') products\nfrom activities\ngroup by sell_date\norder by sell_date\n```\nMS SQL\n```\nselect a.sell_date\n   , count(a.product) num_sold\n   , string_agg(a.product,\',\') within group (order by a.product) products\nfrom (select distinct sell_date,product from activities) a\ngroup by a.sell_date\norder by a.sell_date\n```
['MySQL', 'Oracle']