One problem with strings though is that they might, in the parent post's case, have been editable somewhere. In that case a user (admin user, for example) can u

One problem with strings though is that they might, in the parent post's case, have been editable somewhere. In that case a user (admin user, for example) can unknowingly break the relation. A short string code though, only available from a lookup, for instance, might be acceptable. Since you already have a lookup though, put an int column in there and use the int.