What is a primary key in a dimension table?

Parthiban Kannan

Updated on February 13, 2026

< 1 min read

Primary key is a unique identifier for each record in a dimension table.
It ensures every row can be uniquely referenced from the fact table.
For example, Customer_Dim uses customer_id as the primary key.
The fact table stores this as a foreign key to link transactions.
This relationship lets us analyze sales by specific customers.
Primary keys prevent duplicate dimension records.
They also help BI tools build correct one-to-many relationships.
Without it, filters and aggregations may give wrong results.
So it maintains data integrity and reliable reporting.