Basic concepts

1. G.NIVETHA B.Tech.,
ASSISTANT PROFESSOR
DEPARTMENT OF COMMERCE WITH COMPUTER
APPLICATION
S B K COLLEGE, ARUPPUKOTTAI

2. Database
management
system

3. Understand a DBMS and define its components.
Understand the architecture of a DBMS and its levels.
Distinguish between different database models.
Understand the concept of relational database operations
on a relation.
OBJECTIVES
Use Structured Query Language (SQL) to define simple
relations.

4. DATABASE
MANAGEMENT
SYSTEM

5. 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

6. 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.

7. ARCHITECTURE

8. Database
architecture

9. 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.

10. DATABASE
MODELS

11. 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

12. Hierarchical model
 Data are organized as an upside down tree.
 Each entity has only one parent but can have
several children.

13. Network model
 The entities are organized in a graph.
 Some entities can be accessed through several paths.

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

15. RELATIONAL
MODEL
14.4

16. 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.

17. 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.

18. OPERATIONS
ON
RELATIONS

19. 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

20. Insert operation
 An unary operation.
 Insert a new tuple into the relation.

21. Delete operation
 An unary operation.
 Delete a tuple defined by a criterion from the relation.

22. Update operation
 An unary operation.
 Changes the value of some attributes of a tuple.

23. 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

24. 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.

25. Join operation
 A binary operation.
 Combines two relations based on common attributes.

26. 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.

27. 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.

28. 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.

29. STRUCTURED
QUERY
LANGUAGE

30. 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.

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

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

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

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

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

36. 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

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

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

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

40. OTHER
DATABASE
MODELS

41. 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

42. 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.