Three integrity constraints
Entity integrity
Referential integrity
User-defined integrity
Integrity constraints (or called integrity constraints rules) of general form
IntegrityConstraint :: = (O, P, A, R)
O: Data collection: Object Constraint?
Column, a plurality of rows (tuples), a set of tuples
P: predicate conditions: What kind of constraints?
A: Trigger condition: When inspection?
R: response action: how to do is not satisfied