MySQL 8.0

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

CREATE TABLE article (id INT, art_code VARCHAR(4), art_name VARCHAR(8));
INSERT INTO article VALUES
(1,'5678','computer'),
(2,'0987','display'),
(3,'8547','keyboard');
CREATE TABLE action (id INT, code VARCHAR(4), action VARCHAR(3), qte INT);
INSERT INTO action VALUES
(1,'5678','IN',4),
(2,'0987','OUT',3),
(3,'5678','IN',6),
(4,'5678','OUT',2);
    SELECT id, art_code, art_name, SUM(`IN`) `IN`, SUM(`OUT`) `OUT`
    FROM 
      ( SELECT a0.id, a0.art_code, a0.art_name, SUM(a1.qte) `IN`, NULL `OUT`
        FROM article a0
        LEFT JOIN action a1 ON a0.art_code = a1.code AND a1.action = 'IN'
        GROUP BY a0.id, a0.art_code, a0.art_name
      UNION ALL
        SELECT a0.id, a0.art_code, a0.art_name, NULL, SUM(a2.qte)
        FROM article a0
        LEFT JOIN action a2 ON a0.art_code = a2.code AND a2.action = 'OUT'
        GROUP BY a0.id, a0.art_code, a0.art_name
      ) sq
    GROUP BY id, art_code, art_name
    ORDER BY id;


id
art_code
art_name
IN
OUT


1
5678
computer
10
2

2
0987
display
null
3

3
8547
keyboard
null
null

id	art_code	art_name	IN	OUT
1	5678	computer	10	2
2	0987	display	null	3
3	8547	keyboard	null	null