Re: database design problem.

On Sat, 15 Mar 2014 08:38:03 -0700 (PDT), willy Hakizimana
<willyha24@gmail.com> declaimed the following:

>First of all, this community is amazing at how fast questions are answered.
>I have learned so much.
>
>
>I am designing an app with models that look like this.
>
>Country(country_id(PK), country_name, gdp, gdp_growth, income_per_capita)
>
>Product(product_id(PK), product_name, country_id(FK), imports_volume)
>
>Since I have to show imports_volume for the same product in each country, I
>am stumped on how to design the db.
>
If I understand your statement, you need (paraphrased) the
imports_volume to be for each product for each country...

That means it does NOT belong in either Country or Product tables.

Country(*countryID*, Name, gdp, gdp_growth, per_capita_income)

Product(*productID*, Name)

Imports(_countryID_, _productID_, import_volume)

In Django terms (I believe), this is a many2many relationship using a
via table (the native m2m would create a table with _countryID_,
_productID_ foreign keys only; the via table lets you add data specific to
the relationship itself... An intersect table in older database
terminology)

>
>
--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/

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