Dimension tables provide context for facts.
Characteristics:
- Describe the "who, what, where, when"
- Usually wider (many columns) but fewer rows
- Contain descriptive attributes
- Often have surrogate keys
Common dimensions:
- Date/Time (with fiscal periods, holidays)
- Customer/User
- Product
- Geography
- Employee
Surrogate keys: Use auto-incrementing integers instead of natural keys. Handles changes over time and missing values.