Don't use separator to performance storing a list to achieve one to many.
example
CodeEntertainer
2022-12-18 15:54:37
fk = "1,2,3,4,5"
Hard to maintains the list
Has maximum Solution: build an intersection table. (a.id, b.id) a reference a table pk, b reference b table pk
MYSQL foreign key will automatically indexed and the fk should be reference another table index.