SET('value1','value2',...) [CHARACTER SET charset_name] [COLLATE
collation_name]

A set. A string object that can have zero or more values, each of which
must be chosen from the list of values 'value1', 'value2', ... SET
values are represented internally as integers.

A SET column can have a maximum of 64 distinct members.

The maximum supported length of an individual SET element is M <= 255
and (M x w) <= 1020, where M is the element literal length and w is the
number of bytes required for the maximum-length character in the
character set.

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

