TAILIEUCHUNG - Chapter 2: Constraints, Triggers, Views

Chapter Outline, Declare foreign-key constraints, reference Maintain integrity, restrictions on property and Tuples, modify the constraints, the trigger options in the Design,. the content of the lecture chapter 2 "Constraints, Triggers, Views", invite you to refer for further reference accommodate learning and research. | Chapter 2 Constraints, Triggers, Views Chapter Outline Keys and Foreign Key Constraints on Attributes and Tuples Modification of Constraints Assertion Trigger Views Declaring Foreign-Key Constraints In SQL we may declare an attribute or attributes of one relation to be a foreign key, referencing some attribute(s) of a second relation (possibly the same relation) The referenced attribute(s) of the second relation must be declared UNIQUE or the PRIMARY KEY for their relation. Otherwise, we cannot make the foreign-key declaration. Values of the foreign key appearing in the first relation must also appear in the referenced attributes of some tuple. Two ways to declare a foreign key. Example: Suppose we wish to declare the relation Studio(name, address, presC#) which has a foreign key presC# that references cert# of relation: MovieExec(name, addreses, cert#, netWorth) We may declare presC# directly to reference cert# as follows: CREATE TABLE Studio ( name CHAR(30) .

• Cơ sở dữ liệu
• Declare foreign key constraints
• Reference Maintain integrity
• Restrictions on property and Tuples
• Modify the constraints
• The trigger options in the Design
• Keys and Foreign Key