Question

I have to make a M:1 relationship using SQL Server but I’ve been wondering if the column representing the “many” side should be foreign key and the column representing “one” side should be primary key.
The purpose is retrieving information from the table with the column representing “one” side using the table with the column representing “many” side.
Do you thing this idea is reasonable and would work successfully?

Answer 1

I’ve been wondering if the column representing the “many” side should
be foreign key and the column representing “one” side should be
primary key.

The column representing the many side is indeed a primary key of a table, and the column representing the one side is also a primary key of another table. But there is a new column in one of them, is a foreign key that connect each others(this column is the column that makes the relation many to one, and that is the column you should care of).

So, you have to make them into two tables. Consider the following Many to one example:

Countries and cities relation: One Country has many cities.

This would be represented with two tables:

Countries:

• CountryID primary key,
• Name.

Cities:

• CityID primary key¹,
• CountryId foreign key references Countries(ID),
• Name.

And that is how you should create a many to one relation as follows:

• The columns CountryID and CityID are primary keys in the two tables.
• The column CountryID which represents the one side is a foreign key in the many side(cities table). That is the column that you should

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^{1:You should have a composite key instead of a primary table in the Cities unless you want a city to be in more than one Country at the same time.}