I have 2 tables, a parent (tbl_persons) and a child (tbl_languages_per_person) as follows (a language table is also involved):
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tbl_persons
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* per_id
* per_name
* per_address
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tbl_languages_per_person
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* 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
