# Statistics-based versus hard-wired selectivity

Derby determines the selectivity for a WHERE clause in one of two ways.

- Selectivity from cardinality statistics
- Selectivity from hard-wired assumptions

Parent topic: Selectivity and cardinality statistics
Related concepts
Determinations of rows scanned from disk for a table scan
Estimations of rows scanned from disk for an index scan
What are cardinality statistics?
Working with cardinality statistics