1. Concepts of Database Management, 4th Edition, Pratt & Adamski
Chapter 4
The Relational Model 3:
Advanced Topics
Concepts of Database Management, 4th Edition, Pratt & Adamski

2. Concepts of Database Management, 4th Edition, Pratt & Adamski
Objectives
Define, describe, and use views
Use indexes to improve database performance
Discuss entity, referential, and legal-values integrity
Make changes to the structure of a relational database
Define and use the system catalog
Concepts of Database Management, 4th Edition, Pratt & Adamski

3. Concepts of Database Management, 4th Edition, Pratt & Adamski
Views
Application program’s or individual user’s picture of the database
Less involved than full database
Offers simplification
Provides measure of security
Sensitive tables or columns omitted where not appropriate
Concepts of Database Management, 4th Edition, Pratt & Adamski

4. SQL to Create View Figure 4.1
CREATE VIEW Housewares AS
SELECT PartNum, Description, OnHand, Price
FROM Part
WHERE Class=‘HW’ ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

5. Housewares View of Database
Figure 4.2
Concepts of Database Management, 4th Edition, Pratt & Adamski

6. Concepts of Database Management, 4th Edition, Pratt & Adamski
Query on a View
Selects data only from Tables created in the view
Query is merged with query used to create view
SELECT *
FROM Housewares
WHERE OnHand< 25 ;
Actually executes as
SELECT PartNum, Description, OnHand, Price
FROM Part
WHERE Class=‘HW’
AND OnHand< 25 ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

7. Access Query Design of View
Figures
Concepts of Database Management, 4th Edition, Pratt & Adamski

8. Access Query Design of View with Changed Field Names
Figures
Concepts of Database Management, 4th Edition, Pratt & Adamski

9. SalesCust View SQL Statement
CREATE VIEW
SalesCust (Snum, SLast, SFirst, Cnum, CName) AS
SELECT Rep.RepNum, LastName, FirstName,
CustomerNum, CustomerName
FROM Rep, Customer
WHERE Rep.RepNum=Customer.RepNum ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

10. Concepts of Database Management, 4th Edition, Pratt & Adamski
SalesCust View
Figure 4.7
Concepts of Database Management, 4th Edition, Pratt & Adamski

11. Concepts of Database Management, 4th Edition, Pratt & Adamski
Access Query Design
of SalesCust View
Figure 4.8
Concepts of Database Management, 4th Edition, Pratt & Adamski

12. of SalesCust View (con’t.)
Access Query Design
of SalesCust View (con’t.)
Figure 4.9
Concepts of Database Management, 4th Edition, Pratt & Adamski

13. Concepts of Database Management, 4th Edition, Pratt & Adamski
Advantages of Views
Provides data independence
Same data viewed by different users in different ways
Contains only information required by a given user
Concepts of Database Management, 4th Edition, Pratt & Adamski

14. Concepts of Database Management, 4th Edition, Pratt & Adamski
Indexes
Conceptually similar to book index
Increases data retrieval efficiency
Automatically assigns record numbers
Used by DBMS, not by users
Fields on which index built called Index Key
Concepts of Database Management, 4th Edition, Pratt & Adamski

15. Customer Table with Record Numbers
Figure 4.10
Concepts of Database Management, 4th Edition, Pratt & Adamski

16. Customer Table Index on CustomerNum
Figure 4.11
Concepts of Database Management, 4th Edition, Pratt & Adamski

17. Concepts of Database Management, 4th Edition, Pratt & Adamski
Table Indexes on
CreditLimit, RepNum
Figure 4.12
Concepts of Database Management, 4th Edition, Pratt & Adamski

18. Concepts of Database Management, 4th Edition, Pratt & Adamski
Pros/Cons of Indexes
Can be added or dropped without loss of function
Can make retrieval more efficient
Occupies space that might be required for other functions
DBMS must update index whenever corresponding data are updated
Concepts of Database Management, 4th Edition, Pratt & Adamski

19. Concepts of Database Management, 4th Edition, Pratt & Adamski
SQL to Create Index
CREATE INDEX CustomerName
ON Customer (CustomerName) ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

20. Concepts of Database Management, 4th Edition, Pratt & Adamski
SQL to Delete Index
DROP INDEX RepBal ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

21. Index on Single Field in Access
Figure 4.13
Concepts of Database Management, 4th Edition, Pratt & Adamski

22. Index on Multiple Fields in Access
Figure 4.14
Concepts of Database Management, 4th Edition, Pratt & Adamski

23. Concepts of Database Management, 4th Edition, Pratt & Adamski
Security
Prevention of unauthorized access to database
Two SQL security mechanisms
GRANT provides privileges to users
REVOKE removes privileges from users
GRANT SELECT ON Customer TO JONES ;
REVOKE SELECT ON Customer FROM JONES ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

24. Concepts of Database Management, 4th Edition, Pratt & Adamski
Integrity Rules
Related to foreign keys and primary keys
Defined by Dr. E.F. Codd
Entity integrity
No field that is part of the primary key may accept null values
Referential integrity
If Table A contains a foreign key matching the primary key of Table B, then values must match for some row in Table B or be null
Concepts of Database Management, 4th Edition, Pratt & Adamski

25. Concepts of Database Management, 4th Edition, Pratt & Adamski
Primary Key in Access
Figure 4.15
PRIMARY KEY (CustomerNum)
Concepts of Database Management, 4th Edition, Pratt & Adamski

26. Multi-Field Primary Key in Access
Figure 4.16
PRIMARY KEY (OrderNum, PartNum)
Concepts of Database Management, 4th Edition, Pratt & Adamski

27. Relationships Window to Relate Tables in Access
Figure 4.17
FOREIGN KEY (RepNum) REFERENCES Rep
Concepts of Database Management, 4th Edition, Pratt & Adamski

28. Specifying Referential Integrity
Figure 4.18
Concepts of Database Management, 4th Edition, Pratt & Adamski

29. Violating Referential
Integrity on Adding
Figure 4.19
Concepts of Database Management, 4th Edition, Pratt & Adamski

30. Violating Referential
Integrity on Deleting
Figure 4.20
Concepts of Database Management, 4th Edition, Pratt & Adamski

31. Legal-Values Integrity
States no record can exist with field values other than legal ones
Use SQL CHECK clause
CHECK (CreditLimit IN (5000, 7500, 10000, 15000)) ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

32. Concepts of Database Management, 4th Edition, Pratt & Adamski
Other SQL
Adding new field
ALTER TABLE Customer
ADD CustType CHAR(1) ;
Changing field properties
ALTER TABLE Customer
CHANGE COLUMN CustomerName TO CHAR(50) ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

33. Concepts of Database Management, 4th Edition, Pratt & Adamski
Add Field in Access
Figure 4.22
Concepts of Database Management, 4th Edition, Pratt & Adamski

34. Characteristic in Access
Change Field
Characteristic in Access
Figure 4.23
Concepts of Database Management, 4th Edition, Pratt & Adamski

35. Concepts of Database Management, 4th Edition, Pratt & Adamski
Other SQL
Deleting field
ALTER TABLE Part
DELETE Warehouse ;
Delete SQL Table
DROP TABLE SmallCust ;
Concepts of Database Management, 4th Edition, Pratt & Adamski

36. Concepts of Database Management, 4th Edition, Pratt & Adamski
Delete Field in Access
Figure 4.24
Concepts of Database Management, 4th Edition, Pratt & Adamski

37. Concepts of Database Management, 4th Edition, Pratt & Adamski
Delete Table in Access
Figure 4.25
Concepts of Database Management, 4th Edition, Pratt & Adamski

38. Concepts of Database Management, 4th Edition, Pratt & Adamski
System Catalog
Information about database kept in system catalog
Maintained by DBMS
Example catalog has two tables
Systables
Syscolumns
Concepts of Database Management, 4th Edition, Pratt & Adamski

39. Concepts of Database Management, 4th Edition, Pratt & Adamski
Systables Table
Figure 4.26
Concepts of Database Management, 4th Edition, Pratt & Adamski

40. Partial Syscolumns Table
Figure 4.27
Concepts of Database Management, 4th Edition, Pratt & Adamski