1. Diploma in Software Engineering
Module IV: Database Concepts
Rasan Samarasinghe
ESOFT Computer Studies (pvt) Ltd.
No 68/1, Main Street, Pallegama, Embilipitiya.

2. Contents
1. Introduction to Databases
2. Data
3. Information
4. Database
5. Database System
6. Database Applications
7. Evolution of Databases
8. Traditional Files Based Systems
9. Limitations in Traditional Files
10. The Database Approach
11. Advantages of Database Approach
12. Disadvantages of Database Approach
13. Database Management Systems
14. DBMS Functions
15. Database Architecture
16. ANSI-SPARC 3 Level Architecture
17. The Relational Data Model
18. What is a Relation?
19. Primary Key
20. Cardinality and Degree
21. Relationships
22. Foreign Key
23. Data Integrity
24. Data Dictionary
25. Database Design
26. Requirements Collection and analysis
27. Conceptual Design
28. Logical Design
29. Physical Design
30. Entity Relationship Model
31. A mini-world example
32. Entities
33. Relationships
34. ERD Notations
35. Cardinality
36. Optional Participation
37. Entities and Relationships
38. Attributes
39. Entity Relationship Diagram
40. Entities
41. ERD Showing Weak Entities
42. Super Type / Sub Type Relationships
43. Mapping ERD to Relational
44. Map Regular Entities
45. Map Weak Entities
46. Map Binary Relationships
47. Map Associated Entities
48. Map Unary Relationships

3. Content
49. Map Ternary Relationships
50. Map Supertype/Subtype Relationships
51. Normalization
52. Advantages of Normalization
53. Disadvantages of Normalization
54. Normal Forms
55. Functional Dependency
56. Purchase Order Relation in 0NF
57. Purchase Order Relation in 1NF
58. Purchase Order Relations in 2NF
59. Purchase Order Relations in 3NF
60. Normalized Relations
61. BCNF – Boyce Codd Normal Form
62. Structured Query Language
63. What We Can Do with SQL ?
64. SQL Commands
65. SQL CREATE DATABASE
66. SQL CREATE TABLE
67. SQL DROP
68. SQL Constraints
69. SQL NOT NULL
70. SQL PRIMARY KEY
71. SQL CHECK
72. SQL FOREIGN KEY
73. SQL ALTER TABLE
74. SQL INSERT INTO
75. SQL INSERT INTO SELECT
76. SQL SELECT
77. SQL SELECT DISTINCT
78. SQL WHERE
79. SQL AND & OR
80. SQL ORDER BY
81. SQL UPDATE
82. SQL DELETE
83. SQL LIKE
84. SQL IN
85. SQL BETWEEN
86. SQL INNER JOIN
87. SQL LEFT JOIN
88. SQL RIGHT JOIN
89. SQL UNION
90. SQL AS
91. SQL Aggregate Functions
92. SQL Scalar functions
93. SQL GROUP BY
94. SQL HAVING
95. Database Administration
96. SQL Database Administration

4. Introduction to Databases
Key terms to get know…
• Data ?
• Information ?
• Database ?
• Database System ?

5. Data
Data are numbers, characters, images or other
outputs from devices that is more suitable to
move or process. Data can be known as distinct
types of information.

6. Information
Information is a result of processing and
manipulating and organizing data that adds to
the knowledge of the person receiving it.

7. Database
Database is a collection of interrelated data
items that can be processed by one or more
application systems.

8. Database System
An information system that consists from…
 Database
 DBMS
 Hardware
 Software
 People

9. Database Applications
• Library
• University
• Banking
• Telecommunication
• Sales and Distribution
• Manufacturing
• Human Resources
• Airline

10. Evolution of Databases

11. Types of Database Models

12. Traditional Files Based Systems

13. Limitations in Traditional Files
• Data Redundancy
• Inconsistent Data
• Inflexibility
• Limited Data Sharing
• Poor Data Control
• Security Problems
• Data Isolation

14. The Database Approach

15. Advantages of Database Approach
• Minimal Data Redundancy
• Consistency of Data
• Flexibility
• Sharing of Data
• Data Control
• Proper Security
• Integration of Data
• Ease of Application Development
• Data Manipulation

16. Disadvantages of Database Approach
• Complexity
• Size
• Cost of DBMS
• Additional Hardware Cost
• Higher Impact of a Failure
• Cost of Conversion

17. Database Management Systems (DBMS)
DBMS is a software that enables users to define,
create, maintain and control the access to a
database.

18. DBMS Functions
A. Data Definition
B. Data Entry
C. Data Manipulation
D. Data Display
E. Data Security
F. Data Integrity
G. Backup and Recovery

19. Database Architecture

20. ANSI-SPARC 3 Level Architecture

21. ANSI-SPARC 3 Level Architecture
• External Schema
– Defines the external view of data
as seen by a particular user or
program
• Conceptual Schema
– Defines the logical view of the
data
as seen by all users and programs
• Internal Schema
– Defines the physical view of data
as seen by a DBMS

22. The Relational Data Model
Data elements are stored in different tables
made up of rows and columns. Relates data in
different tables through the use of common
data element(s).

23. What is a Relation?
Data is presented to the user as tables:
• Tables are comprised of rows and a fixed number of
named columns.
• Columns are attributes describing an entity. Each column
must have an unique name and a data type.

24. The Relational Data Model

25. The Relational Data Model

26. The Relational Data Model

27. The Relational Data Model

28. Primary Key
Each table has a primary key. The primary key is
a column or combination of columns that
uniquely identify each row of the table.
(Composite Key)

29. Cardinality and Degree
The cardinality of a table refers to the number of
rows in the table.
The degree of a table refers to the number of
columns.

30. Relationships

31. Relationships
A database is a group of related files.

32. Relationships

33. Foreign Key
A foreign key is a set of columns in one table
that serve as the primary key in another table.

34. Data Integrity
Data Integrity refers to the validity of data.
Problems may encounter!
• Two employees with same NID, EmpNo?
• Employee who is 10 years or 70 years?
• Employee who does not work for you?
Solutions?
• Entity Integrity
• Domain Integrity
• Referential Integrity

35. Data Dictionary
A Data Dictionary is a file or a set of files that
contains a database's metadata.
Names of all tables and their owners.
Names of all indexes and the tables in those
indexes relate.
Constraints defined on tables.

36. Database Design
The database design process can be broken down
into four phases.
Requirements Collection and Analysis
Conceptual Design
Logical Design
Physical Design

37. Requirements Collection and analysis
Prospective database
uses are interviewed to
understand and
document their data
requirements.

38. Conceptual Design
This is high level
description of the
structure of a database.
E.g. E-R diagram

39. Logical Design
This is the process of
mapping the database
structure developed in
the previous phase to a
particular database
model.
E.g. map E-R model to
relational

40. Physical Design
This is the process of
defining structure that
enables the database
to be queried in an
efficient manner.

41. Entity Relationship Model
• An Entity Relationship Model is a data model for describing
the data within databases or information systems.
• It’s a graphical representation of entities and their
relationships to each other.

42. A mini-world example
• A Company is organized in to departments.
• Each department has a number and an
employee who manages the department.
• We keep track of the start date when that
employee started managing the
department.
• A department may have several locations.
• A department controls a number of
projects. Each of which has a name, a
number and a single location.

43. A mini-world example cont’d
• We store each employee’s name, national Id
number, address, salary, birth date and sex.
• An employee is assigned to one
department, but may work on several
projects.
• We keep track of the number of hours per
week that an employee works on each
project.
• We also keep track of the direct supervisor
of each employee.

44. A mini-world example cont’d
• We keep track of the dependants of each
employee for insurance purposes.
• We keep each dependant’s name, sex,
birth date and relationship to the
employee.
Such information is gathered from the
mini-world to perform Phase 1 of
database design process.

45. Entities

46. Relationships

47. Relationships

48. Relationships

49. Relationships

50. Relationships

51. Relationships

52. Relationships

53. Relationships

54. Relationships

55. ERD Notations

56. Cardinality

57. Optional Participation
When the number of participants in the
relationship is zero

58. Entities and Relationships

59. Attributes
• Simple Attribute
• Multi-valued Attribute
• Composite Attribute

60. Attributes
• Derived Attribute
• Identifier
• Composite Identifier

61. Entity Relationship Diagram

62. Entities
• Strong (Regular) Entity
• Weak Entity
• Identifying Relationship

63. ERD Showing Weak Entities

64. Relationships Cont’d
• Unary Relationship
• Ternary Relationship

65. Super Type / Sub Type Relationships

66. Mapping ERD to Relational
Step 1: Map Regular Entities
2: Map Weak Entities
3: Map Binary Relationships
4: Map Associated Entities
5: Map Unary Relationships
6: Map Ternary (and n-ary) Relationships
7: Map Supertype/Subtype Relationships

67. 1: Map Regular Entities

68. 1: Map Regular Entities
Project (Proj_No, Location, Proj_Name)

69. 2: Map Weak Entities

70. 3: Map Binary Relationships
1. Map Binary One-to-Many Relationships
2. Map Binary Many-to-Many Relationships
3. Map Binary One-to-One Relationships

71. 3.1 Map Binary One-to-Many Relationships

72. 3.1 Map Binary One-to-Many Relationships

73. 3.2 Map Binary Many-to-Many Relationships

74. 3.3 Map Binary One-to-One Relationships

75. 4: Map Associated Entities

76. 5: Map Unary Relationships

77. 6: Map Ternary (and n-ary) Relationships

78. 7: Map Supertype/Subtype Relationships

79. Normalization
• In relational database design, the process of
organizing data to minimize redundancy.
• Normalization usually involves dividing a
database into two or more tables and defining
relationships between the tables.

80. Advantages of Normalization
Reduction of data redundancy within tables:
 Reduce data storage space.
 Reduce inconsistency of data.
 Remove insert, update and delete anomalies.
 Improve flexibility of the system.

81. Disadvantages of Normalization
Reduction in efficiency of certain data retrieval
as relations may be joined during retrieval.
• Increase join
• Increase use of indexes: storage (keys)
• Increase complexity of the system

82. Normal Forms
 1NF any multi-valued attributes have been
removed
 2NF any partial functional dependencies have
been removed
 3NF any transitive dependencies have been
removed
 BCNF any remaining anomalies that result
from functional dependencies have been
removed

83. Functional Dependency
Functional Dependency is a constraint between two
attributes or two sets of attributes
The functional dependency of B on A is represented
by an arrow: A → B
e.g.
NID → Name, Address, Birth date
VID → Model, Color
ISBN → Title, Author, Publisher

84. Purchase Order Relation in 0NF

85. First Normal Form - 1NF
• No multi valued columns exists.
• All the key attributes are defined.
• All non-key attributes are fully functionally
dependent on the primary key.

86. Purchase Order Relation in 0NF

87. Purchase Order Relation in 0NF

88. 1NF - Actions Required
1. Examine for repeat groups of data
2. Remove repeat groups from relation
3. Create new relation(s) to include repeated
data
4. Include key of the 0NF to the new relation(s)
5. Determine key of the new relation(s)

89. Purchase Order Relation in 0NF

90. Purchase Order Relation in 1NF

91. Purchase Order Relation in 1NF

92. Purchase Order Relation in 1NF

93. Problems - 1NF
INSERT PROBLEM
Cannot know available parts until an order is placed
(e.g. P4 is bush)
DELETE PROBLEM
Loose information of part P7 if we cancel purchase order
115 (e.g. Delete PO-PART for Part No P7)
UPDATE PROBLEM:
To change description of Part P3 we need to change every
record in PO-PART containing Part No P3

94. Second Normal Form - 2NF
• Relations should not contain any partial
functional dependencies.
• E.g. No attribute is dependent on only a
partial of the primary key.

95. PO-PART Relation (Parts Ordered) in 1NF
Part Description is depended only on Part No,
which is part of the key of PO-PART.

96. Parts Ordered Relation in 1NF

97. 2NF - Actions Required
If entity has a concatenated key
1. Check each attribute against the whole key
2. Remove attribute and partial key to new
relation
3. Optimize relations - consider combining
tables that have identical primary keys

98. Parts Ordered Relation in 1NF

99. Parts Ordered Relations in 2NF

100. Purchase Order Relations in 2NF

101. Purchase Order Relation in 2NF

102. Problems - 2NF
INSERT PROBLEM
Cannot know available suppliers until an order is placed
(e.g. 200 is hardware stores)
DELETE PROBLEM
Loose information of supplier 100 if we cancel purchase
order 116 (e.g. Delete PO for Supplier No 100)
UPDATE PROBLEM
To change name of Supplier 222 we need to change every
record in PO containing Supplier No 222

103.