MySQL 8.0

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CREATE TABLE purchase
             (customerid integer,
              orderid integer,
              item varchar(16),
              category varchar(16),
              purdate date,
              sold integer,
              price integer);
INSERT INTO purchase
            (customerid,
             orderid,
             item,
             category,
             purdate,
             sold,
             price)
            VALUES (1, 1, 'book', 'stationary', '2018-01-01', 1, 5),
                   (2, 2, 'ball', 'toys', '2018-01-01', 2, 2),
                   (3, 3, 'shirt', 'cloth', '2018-01-01', 1, 10),
                   (1, 4, 'pen', 'stationary', '2018-01-01', 5, 3),
                   (4, 5, 'shirt', 'cloth', '2018-01-01', 2, 10),
                   (5, 6, 'card', 'stationary', '2018-01-02', 15, 2),
                   (6, 7, 'tshirt', 'cloth', '2018-01-02', 3, 7),
                   (2, 8, 'book', 'stationary', '2018-01-03', 6, 5),
                   (3, 9, 'car', 'toys', '2018-01-03', 2, 4),
                   (1, 10, 'book', 'stationary', '2018-01-03', 4, 5),
                   (4, 11, 'ball', 'toys', '2018-01-04', 2, 2),
                   (7, 12, 'notebk', 'stationary', '2018-01-04', 2, 3);
SELECT purdate,
       category,
       item,
       total,
       revenue
       FROM (SELECT purdate,
                    category,
                    item,
                    sum(sold) total,
                    sum(sold) * price revenue,
                    rank() OVER (PARTITION BY purdate
                                 ORDER BY sum(sold) DESC) r
                    FROM purchase
                    GROUP BY purdate,
                             category,
                             item,
                             price) x
       WHERE r = 1
       ORDER BY purdate;


purdate
category
item
total
revenue


2018-01-01
stationary
pen
5
15

2018-01-02
stationary
card
15
30

2018-01-03
stationary
book
10
50

2018-01-04
toys
ball
2
4

2018-01-04
stationary
notebk
2
6

purdate	category	item	total	revenue
2018-01-01	stationary	pen	5	15
2018-01-02	stationary	card	15	30
2018-01-03	stationary	book	10	50
2018-01-04	toys	ball	2	4
2018-01-04	stationary	notebk	2	6