The document discusses database management systems (DBMS) and their components, architecture, and models. It describes the relational database model and common operations on relations like select, project, join, union, intersection, and difference. It also introduces the structured query language (SQL) used to perform operations on relational databases and briefly discusses other database models like distributed and object-oriented databases.

1. Chapter 14
Databases

2. Understand aUnderstand a DBMSDBMS and define its components.and define its components.
Understand the architecture of a DBMS and its levels.Understand the architecture of a DBMS and its levels.
Distinguish between differentDistinguish between different database modelsdatabase models..
Understand the concept ofUnderstand the concept of relational databaserelational database operationsoperations
on a relation.on a relation.
After reading this chapter, the reader shouldAfter reading this chapter, the reader should
be able to:be able to:
OOBJECTIVESBJECTIVES
UseUse Structured Query Language (SQL)Structured Query Language (SQL) to define simpleto define simple
relations.relations.

3. DATABASEDATABASE
MANAGEMENTMANAGEMENT
SYSTEMSYSTEM
14.114.1

4. DBMS
 Database – a collection of data that is logically
coherent.
 DBMS – Database Management System
 defines, creates, and maintains a database.
 Allows users controlled access to data in the database.
 A combination of 5 components:
 Hardware
 Software
 Data
 Users
 Procedures

5. Figure 14-1 DBMS components
 Hardware –
the physical computer system that allows physical access to data.
 Software –
the actual program that allows users to access, maintain, and update
physical data.
 Data – stored physically on the storage devices
 Users –
 End users - Normal user and DBA (Database Administrator)
 Application programs
 Procedures –
a set of rules that should be clearly defined and followed by the users.

6. ARCHITECTUREARCHITECTURE
14.214.2

7. Figure 14-2
Database
architecture

8. Architecture
 Internal level –
 Determines where data are actually stored on the
storage device.
 Low-level access method
 Conceptual level –
 Defines the logical view of the data
 The main functions of DBMS are in this level.
 External level –
 Interacts directly with the user.
 Change the data coming from the conceptual level to
a format and view that are familiar to the users.

9. DATABASEDATABASE
MODELSMODELS
14.314.3

10. Database models
 A database model
 defines the logical design of data.
 Describes the relationships between different
parts of data.
 3 models
 Hierarchical model
 Network model
 Relational model

11. Figure 14-3 Hierarchical model
 Data are organized as an upside down tree.
 Each entity has only one parent but can have
several children.

12. Figure 14-4
Network model
 The entities are organized in a graph.
 Some entities can be accessed through several
paths.

13. Figure 14-5
Relational model
 Data are organized in two-dimensional tables called
relations.
 The tables are related to each other.
 The most popular model.

14. RELATIONALRELATIONAL
MODELMODEL
14.414.4

15. Relational model
 RDBMS (Relational Database Management System)
 external view
 The data are represented as a set of relations.
 A relation is a two-dimensional table.
 This doesn’t mean that data are stored as tables;
the physical storage of the data is independent of
the way the data are logically organized.

16. Figure 14-6
Relation
 Name – each relation in a relational database should have a name that is
unique among other relations.
 Attribute – each column in a relation.
 The degree of the relation – the total number of attributes for a relation.
 Tuple – each row in a relation.
 The cardinality of the relation – the total number of rows in a relation.

17. OPERATIONSOPERATIONS
ONON
RELATIONSRELATIONS
14.514.5

18. Operations on relations
 In a relational database, we can define several operations
to create new relations out of the existing ones.
 Basic operations:
 Insert
 Delete
 Update
 Select
 Project
 Join
 Union
 Intersection
 Difference

19. Figure 14-7 Insert operation
 An unary operation.
 Insert a new tuple into the relation.

20. Figure 14-8
Delete operation
 An unary operation.
 Delete a tuple defined by a criterion from the relation.

21. Figure 14-9
Update operation
 An unary operation.
 Changes the value of some attributes of a tuple.

22. Figure 14-10 Select operation
 An unary operation.
 It is applied to one single relation and creates another
relation.
 The tuples in the resulting relation are a subset of the tuples
in the original relation.
 Use some criteria to select

23. Figure 14-11 Project operation
 An unary operation.
 It is applied to one single relation and creates another
relation.
 The attributes in the resulting relation are a subset of the
attributes in the original relation.

24. Figure 14-12 Join operation
 A binary operation.
 Combines two relations based on common attributes.

25. Figure 14-13
Union operation
 A binary operation.
 Creates a new relation in which each tuple is either in the
first relation, in the second, or in both.
 The two relations must have the same attributes.

26. Figure 14-14 Intersection operation
 A binary operation.
 Creates a new relation in which each tuple is a member in
both relations.
 The two relations must have the same attributes.

27. Figure 14-15
Difference operation
 A binary operation.
 Creates a new relation in which each tuple is in the first
relation but not the second.
 The two relations must have the same attributes.

28. STRUCTUREDSTRUCTURED
QUERYQUERY
LANGUAGELANGUAGE
14.614.6

29. SQL (Structured Query Language)
 Standardized by ANSI and ISO for use on
relational databases.
 It is a declarative (not procedural) language,
which means that the users declare what they
want without having to write a step-by-step
procedure.
 First implemented by Oracle in 1979.
 SQL allows you to combine the following
statements to extract more complex information
from database.

30. Insert
 insert into RELATION-NAME
values ( … , … , … )
 insert into COURSES
values ( “CIS52”,”TCP/IP”, 6 )

31. Delete
 delete from RELATION-NAME
where criteria
 delete from COURSES
where No=“CIS19”

32. Update
 update RELATION-NAME
set attribute1=value1, attribute2=value2, …
where criteria
 update COURSES
set Unit=6
where No=“CIS51”

33. Select
 select *
from RELATION-NAME
where criteria
 select *
from COURSES
where Unit=5

34. Project
 select attribute-list
from RELATION-NAME
 select No, Unit
from COURSES

35. Join
 select attribute-list
from RELATION1,RELATION2
where criteria
 select No,Course-Name,Unit,Professor
from COURSES,TAUGHT-BY
where COURSES.No=TAUGHT-BY.No

36. Union
 select *
from RELATION1
union
select *
from RELATION2
 select *
from CIS15-Roster
union
select *
from CIS52-Roster

37. Intersection
 select *
from RELATION1
intersection
select *
from RELATION2
 select *
from CIS15-Roster
intersection
select *
from CIS52-Roster

38. Difference
 select *
from RELATION1
minus
select *
from RELATION2
 select *
from CIS15-Roster
minus
select *
from CIS52-Roster

39. OTHEROTHER
DATABASEDATABASE
MODELSMODELS
14.714.7

40. Distributed databases
 It is not a new model. It is based on relational model.
 The data are stored on several computers that
communicate through the Internet or some private
WAN.
 Data are either fragmented, with each fragment
stored at one site, or data are replicated at each site.
 Fragmented distributed databases
 Replicated distributed databases

41. Object-Oriented databases
 Some application like to see data as a
structure such as a record made of fields.
 Tries to keep the adv. of the relational model
and allows applications to access structured
data.
 In an OODB, objects and their relations are
defined. In addition, each object can have
attributes that can be expressed as fields.