Can one relation column update another automatically in the other direction?
eg. packages can have many books. books can belong to many packages. If I have two relation columns in each table, and add a book to a package, can the packages row update its multiple relation column to add the book?
Relations look for matching values. If a match is found, then a relation is formed. If you add a row in either table, that causes another match in any of the relations, then that will be reflected in those relations. They are dynamic based if the data they are relating.