MySQL 8.0

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-- табл
CREATE TABLE calc (id INT, 
                   sm int);
INSERT INTO calc (id, sm) 
VALUES 
(1,10), (1, -10), 
(2,5), (2,7), 
(4,1), (4,5), (4,-5), (4,-5);
SELECT id, sm FROM calc;

Records: 8  Duplicates: 0  Warnings: 0




id
sm


1
10

1
-10

2
5

2
7

4
1

4
5

4
-5

4
-5


select group_concat(c.id) from calc as c  limit 2 


group_concat(c.id)


1,1,2,2,4,4,4,4