Syntax:
MAKE_SET(bits,str1,str2,...)

Returns a set value (a string containing substrings separated by ,
characters) consisting of the strings that have the corresponding bit
in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL
values in str1, str2, ... are not appended to the result.

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

