Three Characteristics of DB constraints:

1. Event (insert, update, delete)
2. Condition
3. Action

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• Built-in constraints: system-defined condition + system-defined action
  • Defined when a table is created

Example:

	CREATE TABLE Student(
		Sid NUMBER (5) CONSTRAINT Pk_student PRIMARY KEY,
		Sname VARCHAR2 (30),
		gpa NUMBER
	)

• Assertion: user-defined condition + system-defined action
• Triggers: both condition and action are user-defined