Adding foreign keys

Foreign key references are essential to both the snowflake and star schema. When creating either of these schemas, correctly setting up the foreign keys is vital because they connect dimensions to the fact table. They also enforce a one-to-many relationship, because unless otherwise specified, a foreign key can appear more than once in a table and primary key can appear only once.

The fact_booksales table has three foreign keys: book_id, time_id, and store_id. In this exercise, the four tables that make up the star schema below have been loaded. However, the foreign keys still need to be added.

In the constraint called sales_book, set book_id as a foreign key.
In the constraint called sales_time, set time_id as a foreign key.
In the constraint called sales_store, set store_id as a foreign key.

Exercise

Adding foreign keys

Instructions