The Primary Key (PK) is the set of fields that uniquely identify a row in your table.
Concrete examples:
Daily metrics table (fact table)
Primary Key: (date, campaign_id, ad_id)
2025-01-15
camp_123
ad_456
1000
50
ad_789
800
30
Each combination (date + campaign_id + ad_id) identifies a unique row.
Campaign attributes table (dimension table)
Primary Key: (campaign_id)
Summer Campaign
ACTIVE
5000
camp_456
Winter Campaign
PAUSED
3000
Each campaign_id identifies a unique campaign.
Why is this important?
The Primary Key concept allows you to define which table attributes identify each row as unique. This is essential for:
Determining the behavior of the UPSERT method: should an existing row be updated or should a new row be inserted?
Avoiding duplicates in your tables
Guaranteeing the uniqueness of each row and data integrity, two essential concepts in data management
