I have 2 tables, a parent (tbl_persons) and a child (tbl_languages_per_person) as follows (a language table is also involved):
------------------ tbl_persons ------------------ * per_id * per_name * per_address -------------------------------------- tbl_languages_per_person -------------------------------------- * lpp_person_id * lpp_language_id * lpp_id As you can see, there is an obvious key in the child table which is "lpp_person_id + lpp_language_id", but I also need the field "lpp_id" as a unique key which is a field that contains a consecutive number of type serial. My question is: what should I configure as the primary key, "lpp_person_id + lpp_language_id" or "lpp_id"? Is the role of a primary key different from that of a unique index? With respect, Jorge Maldonado
