VERSION A What does modality refer to? How does it appear on ER diagram? - ANSWERRefers to the MINIMUM number of times an instance in one entity can be associated with instance of another entity (minima) Appears as a 0 or 1 on the relationship line, next to cardinality Define: Referential Integrity - ANSWER- Requires that ALL foreign key values must either be fully NULL or match some primary key value 4 Ways Referential Integrity can be violated: - ANSWER- 1. Primary key is updated 2. Foreign key is updated 3. Row containing primary key is DELETED 4. Row containing foreign key is INSERTED 4 Actions to Correct Referential Integrity Violation: - ANSWER- 1. RESTRICT - rejects an insert, update, or delete 2. SET NULL - sets invalid foreign keys to null 3. SET DEFAULT - sets invalid foreign keys to a default primary value 4. CASCADE - propagates primary key changes to foreign keys What is an important aspect to referential integrity? - ANSWER- reference to data in one relation is based on values in another relation