MySQL:

GROUP_CONCAT

Syntax:
GROUP_CONCAT(expr)

This function returns a string result with the concatenated non-NULL
values from a group. It returns NULL if there are no non-NULL values.
The full syntax is as follows:

GROUP_CONCAT([DISTINCT] expr [,expr ...]
[ORDER BY {unsigned_integer | col_name | expr}
[ASC | DESC] [,col_name ...]]
[SEPARATOR str_val])

URL: https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html

Example

mysql> SELECT student_name,
GROUP_CONCAT(test_score)
FROM student
GROUP BY student_name;