MySQL 8.0

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CREATE TABLE mytable2(id int, pos int, value int)
INSERT INTO mytable2 VALUES (1,1,1),(1,2,2),(1,3,3),(1,4,4),(1,5,5),(1,6,6)

Records: 6  Duplicates: 0  Warnings: 0


CREATE TABLE mytable(id int, pt1 int, pt2 int, pt3 int, pt4 int, pt5 int, pt6 int)
CREATE PROCEDURE `new_routine` (_id int, _sequence int, _pt1 int, _pt2 int,_pt3 int)
BEGIN

    IF _sequence = 0 then
       SET @sql := CONCAT('INSERT INTO mytable (id,pt1,pt2,pt3) VALUES (',_id,',',_pt1,',',_pt2,',',_pt3,')');
    ELSE
       SET @sql := CONCAT('UPDATE mytable SET pt',1 +((_sequence -1) * 3) ,'= ',_pt1
                          ,', pt',2 +((_sequence -1) * 3) ,'= ',_pt2
                          ,', pt',3 +((_sequence -1) * 3) ,'= ',_pt3,' WHERE id = ',_id);
    END IF;

    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
END
CALL new_routine(1,0,1,1,1);

CALL new_routine(1,1,2,2,2)
CALL new_routine(1,2,3,3,3)
SELECT * FROM mytable


id
pt1
pt2
pt3
pt4
pt5
pt6


1
2
2
2
3
3
3


SELECT * FROM mytable2


id
pos
value


1
1
1

1
2
2

1
3
3

1
4
4

1
5
5

1
6
6