9.3. State Transition Tables
When most newbies think of constraints, they know only static column constraints, such as NOT NULL, DEFAULT, and CHECK () clauses. A little bit later, they will learn about simple declarative referential integrity (DRI) constraints. That means simple PRIMARY KEY and REFERENCES clauses with some simple actions to bring the database to a state consistent with business rules.
The bad news is that there are not enough SQL constructs for all business rules. A transition constraint says that an entity can be updated only in certain ways. These constraints are often modeled as a state transition diagram. There is an initial state, flow lines that show what the next legal state(s) are, and one or more termination states. ...
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