MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE mytable (
  unique_1 int,
  unique_2 varchar(25), 
  Number int
);

insert into mytable values
(222, 'MIN', 1),
(222, 'MIN', 2),
(222, 'MAX', 1),
(333, 'MIN', 1),
(333, 'MAX', 2),
(444, 'MAX', 1),
(444, 'MAX', 2),
(444, 'MAX', 3);

Records: 8  Duplicates: 0  Warnings: 0


SELECT unique_1, MIN(case when unique_2 = 'MIN' then Number end) AS minVal,
                 MAX(case when unique_2 = 'MAX' then Number end) AS maxVal
FROM mytable
group by unique_1


unique_1
minVal
maxVal


222
1
1

333
1
2

444
null
3


SELECT unique_1, CASE WHEN minVal IS NOT NULL THEN 'MIN' ELSE 'MAX' END AS 'unique_2',
       COALESCE(minVal, maxVal) as number
FROM (
  SELECT unique_1, MIN(CASE WHEN unique_2 = 'MIN' THEN Number END) AS minVal,
                   MAX(CASE WHEN unique_2 = 'MAX' THEN Number END) AS maxVal
  FROM mytable
  group by unique_1
) AS s


unique_1
unique_2
number


222
MIN
1

333
MIN
1

444
MAX
3