Question

I need a table City for my database model, I have two possible designs:

City:
    id_city   PK
    city
    country


City:
    city
    country
    PRIMARY KEY(city, country)

I am wondering what would be more appropriate. In case 1 I could insert a city twice with a different primary key…Right? The case two appears to be more correct…isn’t? What you recommend me?

Answer 1

I would suggest the following:

City:
    id_city   PK
    city
    country
    UNIQUE Constraint(city, country)

Why?

1. Need more software controls/logic to have a string key vs. an
   integer/number
2. DB operations on integer/number keys is faster
3. More support for auto generation of such key (in db engines and JPA
   for example)
4. If for some weird reason the city name changes it’ll
   break the database integrity.

Just my 2 cents.