Updates to Multi-Table Views
A UNION B:
- Inserted tuple goes into A if it satisfies A’s definition and into B if it satisfies B’s definition (A, B can be views or base tables; at least one must be satisfied)
- Deleted tuples deleted from both A and B
- Update = atomic (delete, insert) sequence
- Example: RichEmps UNION SeattleEmps = RichSeattleEmps