Use a comma-separated field in another SQL query
It's a very weird database schema in the first place.

There should be never a thing like comma-separated values in one cell. Learn the database normalization and then create a link table wghich can be used to get all your records in a single query with JOIN.

There should be never a thing like multiple tables of the same structure. there should be only one table with a field to distinguish the kind of domain.