CIST-1200- Database Management:THE RELATIONAL MODEL 2: INDEXES

CIST-1200- Database Management

Chapter 4: THE RELATIONAL MODEL 2: INDEXES
Lecture 4-B

DUE: SEP 30

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1. What are views?
Views are application program’s or individual user’s picture of the database
Less involved than full database
Simplification
Security

Example:
CREATE VIEW Housewares AS
SELECT PartNum, Description, OnHand, Price
FROM Part
WHERE Class='HW';


2. How indexes improve database performance?

Indexes improve performance by using Record numbers automatically assigned and used by DBMS to Increase data retrieval efficiency


Example:
CREATE INDEX CustomerName ON Customer (CustomerName);


3. Explain the security features of a DBMS
Prevention of unauthorized access to database
GRANT SELECT ON Customer TO Jones;

Example to cancel
REVOKE SELECT ON Customer FROM Jones;


 4. What is entity?
Name of place, things, persons to track in database called a table

5. What is  referential integrity?

if table-A contains a foreign key that matches the primary key of table-B, the values of this foreign key must match the value of the
primary key for some row in table B or be null

Example to create non existence foreign Key

FOREIGN KEY (RepNum) REFERENCES Rep


6. What is  legal-values integrity?

A set of values allowable in a field

Example:
CHECK (CreditLimit IN (5000, 7500, 10000, 15000))