> 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 > > > > > >
