MariaDB 10.3

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table data_usage
(
    time     timestamp default current_timestamp() not null on update current_timestamp(),
    mac      varchar(32)                           not null,
    download bigint    default 0                   not null,
    upload   bigint    default 0                   not null
);
insert into data_usage values 
('2021-04-10', 'xx', 612545, 51234), 
('2021-04-11', 'yy', 91243, 89), 
('2021-04-12', 'xx', 19832, 234), 
('2021-04-13', 'xx', 90781234, 78), 
('2021-04-14', 'xx', 928741, 2134), 
('2021-04-15', 'yy', 813724, 789), 
('2021-04-16', 'xx', 2897345, 634), 
('2021-04-17', 'yy', 1923, 2345), 
('2021-04-18', 'yy', 9182, 56089), 
('2021-04-19', 'xx', 13948245, 9023)
SELECT SUM(download) AS downloads,
       SUM(upload) AS uploads,
       SUM(download + upload) AS total
FROM data_usage
WHERE time >= CURDATE() - INTERVAL DAY(CURDATE()) - 13 DAY - INTERVAL IF(DAY(CURDATE()) < 13, 1, 0) MONTH


downloads
uploads
total


109380394
71092
109451486


SELECT mac,
       SUM(download) AS downloads,
       SUM(upload) AS uploads,
       SUM(download + upload) AS total
FROM data_usage
WHERE time >= CURDATE() - INTERVAL DAY(CURDATE()) - 13 DAY - INTERVAL IF(DAY(CURDATE()) < 13, 1, 0) MONTH
GROUP BY mac


mac
downloads
uploads
total


xx
108555565
11869
108567434

yy
824829
59223
884052


SELECT COALESCE(mac, 'Total') AS mac,
       SUM(download) AS downloads,
       SUM(upload) AS uploads,
       SUM(download + upload) AS total
FROM data_usage
WHERE time >= CURDATE() - INTERVAL DAY(CURDATE()) - 13 DAY - INTERVAL IF(DAY(CURDATE()) < 13, 1, 0) MONTH
GROUP BY mac WITH ROLLUP


mac
downloads
uploads
total


xx
108555565
11869
108567434

yy
824829
59223
884052

Total
109380394
71092
109451486

mac	downloads	uploads	total
xx	108555565	11869	108567434
yy	824829	59223	884052
Total	109380394	71092	109451486