(Introduction to database system | Wang Shan) Chapter V database integrity: Exercises

【 answer 】

Integrity constraints ： It refers to the semantic constraints that the data in the database should meet . Generally, it can be divided into six categories ：

• Static column level constraints
• Static tuple constraint
• Static relationship constraints
• Dynamic column level constraints
• Dynamic tuple constraint
• Dynamic relationship constraints

① Static column level constraint is a description of the value field of a column , It includes the following aspects :

• Yes data type Constraints , Including the type of data 、 length 、 Company 、 Precision etc.

• Yes data format Constraints

• Yes Value range or value set Constraints

• Yes Null value Constraints

• Other constraints

② Static tuple constraint is to specify the constraint relationship between the columns that make up a tuple , Static tuple constraints are limited to a single tuple

③ Static relation constraint is that there are various connections or constraints between the tuples of a relation or between several relations , Common static relationship constraints are

• Entity integrity constraints
• Refer to integrity constraints
• Functional dependency constraints

④ Dynamic column level constraints are the constraints that should be met when modifying column definitions or column values , Including the following two aspects :

• Constraints when modifying column definitions
• Constraints when modifying column values

⑤ Dynamic tuple constraint refers to the need to refer to its old value when modifying the value of a tuple , And some constraints need to be met between the old and new values

⑥ Dynamic relationship constraints are constraints placed on the state before and after the relationship changes , For example, transaction consistency 、 Constraints such as atomicity

【 answer 】

• Whether the outer code can be null
• The following updates need to be considered 、 Delete the question
  

CREATE TABLE Dept
(
	Dept NUMBER(4) PRIMARY KEY,
	Name VARCHAR(10),
	Manager_name VARCHAR(10),
	Phone NUMBER(11)
);

CREATE TABLE Worker
(
	Nol NUMBER(4) PRIMARY KEY,
	Name VARCHAR(10),
	Age NUMBER(4) CHECK(W_age <= 60),
	Job VARCHAR(10),
	Wages NUMBER(7,2),
	Deptno NUMBER(10),
	
	FOREIGN KEY(W_deptno) REFERENCES Dept(Deptno)
);

【 answer 】

Entity integrity

Referential integrity