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Chapter Five Physical Database Design.pptx
1.
2. 1. Planning: that is identifying information gap in an organization and
propose a database solution to solve the problem.
2. Analysis: Concentrates more on fact finding about the problem or the
opportunity.
Feasibility analysis, requirement determination and
structuring, and selection of best design method are also
performed at this phase.
3. Design: in database designing more emphasis is given to this phase. The
phase is further divided into three sub-phases.
Conceptual Design, Logical Design, Physical Design:
4. Implementation: the testing and deployment of the designed database
for use.
5. Operation and Support: administering and maintaining the operation
of the database system and providing support to users.
3. is the process of coming up with different
kinds of specification for the data to be
stored in the database.
is one of the middle phases we have in
information systems development
Deals with describing how the data should be
perceived at different levels and finally how
it is going to be stored in a computer system.
5. is the process of constructing a model of the
information used in an enterprise,
independent of any physical considerations.
is source of information for logical design
Mostly uses ER Model to describe the data .
refinement of the schema, which is
verification of Entities, Attributes, and
Relationships
6. Conceptual design revolves around
discovering and analyzing organizational and
user data requirements
The important activities are to identify
Entities
Attributes
Relationships
Constraints
And based on these components develop the
ER model using
ER diagrams
7. Entity-Relationship modeling is used to
represent conceptual view of the database
The main components of ER Modeling are:
Entities
Represented by Rectangle
Attributes
Represented by Oval
Relationships
Represented by Diamond
Constraints
Represent the constraint in the data
8. is the process of constructing a model of the
information based on a specific data model,
independent of DBMS and other physical
considerations.
Normalization process
Collection of Rules to be maintained
Discover new entities in the process
Revise attributes based on the rules and the
discovered Entities
9. The first step before applying the rules in relational data
model is converting the conceptual design to a form
suitable for relational logical model, which is in a form of
tables.
Converting ER Diagram to Relational Tables
Three basic rules to convert ER into tables or relations:
Rule 1: Entity Names will automatically be table names
Rule 2: Mapping of attributes: attributes will be columns of
the respective tables.
Atomic or single-valued or derived or stored attributes will be
columns
Composite attributes: the parent attribute will be ignored and the
decomposed attributes (child attributes) will be columns of the
table.
Multi-valued attributes: will be mapped to a new table where the
primary key of the main table will be posted for cross referencing.
Rule 3: Relationships: relationship will be mapped by using a
foreign key attribute.
Foreign key is a primary or candidate key of one relation used to
create association between tables.
10. Refinement: eliminates inconsistency,
ambiguity and redundancy.
Identifies relations based on primary key
Decompose relations with anomalies to produce
smaller, well-structured relations
1. Insertion Anomalies
2. Deletion Anomalies
3. Modification Anomalies
11. Defines specific storage or access methods
used by database
Tailored to a specific DBMS system –
Includes estimate of storage space
12. Physical design describes the base relation,
file organization, and indexes used to
achieve efficient access to the data, and any
associated integrity constraints and security
measures.
Logical database design is concerned with
the what; physical database design is
concerned with the how.
13.
14. A good human computer interface
provides a unifying structure for finding,
viewing and invoking the different
components of a system.
These are the means or methods by which
users interact with the system.
Interface may be designed to allow:
Command based interactions
Menu based interaction
Object based interaction: icons, symbols
Natural language interaction
15. Meaningful title
Comprehensible instructions
Logical grouping and sequencing of fields
visually appealing layout of the form/report
familiar field labels
consistent terminology and abbreviation
consistent use of color
visible space and boundaries or data entry fields
convenient cursor movement
error correction for individual characters and entire
fields
error massage for unacceptable fields
optional field marked clearly
explanatory massages for fields
completion signal
16.
17. 17
The two fundamental concepts that need to be
considered while designing database systems are:
Maintaining the consistency of the database to all the
changes, and
Protecting the database from unauthorized users.
18. 18
Integrity constraints ensure that the changes made
to the database by authorized users do not result in
a loss of data consistency.
It is a predicate to the database that needs to be
declared at all time.
Types of Constraints
Key Constraints (Entity Integrity)
Foreign Key Constraints (Referential Integrity)
Domain Constraints (Domain Integrity)
General Constraints (User Defined Integrity)
19. 19
A domain constraint is a predicate on an attribute A
of each tuple of a relation to be atomic value from
a domain set domain(A).
Syntax:
CREATE DOMAIN <domain_name> <data_type>
CONSTRAINT <constraint_name> CHECK <constraint>
The CHECK statement can also be
directly applied to a column without defining a domain,
in a table definition as a tuple based constraint
CHECK (<logical_expression>)
21. 21
User defined constraint is an assertion defined by
the user requirement.
Domain and Referential integrity constraints.
The syntax for general assertion is:
CREATE ASSERTION <assertion_name> CHECK <predicate>
Example
CREATE ASSERTION NumberOfTeamMembers CHECK (8 >=
ALL (SELECT EmpId FROM EmpTeams GROUP BY TeamId)
22. 22
Triggers are statements that the database
management system executes automatically in
response to a modification to the database.
Triggers need to specify:
The event that will cause or initiate the trigger
execution,
Condition to be specified for the trigger execution to
proceed, and
The action to be taken in response.
action
condition
event
?
23. 23
The trigger events are:
INSERT, DELETE, UPDATE and SELECT.
The actions for the triggers may be taken:
After successful completion of the operation (event): AFTER
Before the execution of the operation (event): BEFORE (INSTEAD OF)
Syntax
CREATE TRIGGER <trigger_name>
ON {<table>|<view>}
{FOR | AFTER | INSTEAD OF} {[INSERT] | [UPDATE] | [DELETE] |
[SELECT]}
AS
<SQL_Statement>
24. 24
Create a trigger that inserts the employee id to the
fulltime employee table if the employee is a
fulltime employee otherwise in the part-time
employee table
CREATE TRIGGER EmployeeType
ON [Employees]
AFTER INSERT
AS
If (SELECT empType From inserted) = 1
INSERT INTO [fulltimeEmployees] (empId)
SELECT empId FROM inserted
ELSE
INSERT INTO [parttimeEmployees] (empId)
SELECT empId FROM inserted
25. 25
Database security refers to protection of the database from malicious
access such as:
Unauthorized reading of data,
Unauthorized modification of data, and
Unauthorized destruction of data.
Some of the threats to the database because of malicious access are:
Loss of integrity,
Loss of availability,
Loss of confidentiality
Security measure levels
Database System,
Operating System,
Network,
Physical,
Human
26. 26
Database system security can be implemented with
the use of:
Account and Role Creation,
Privilege granting,
Privilege revocation, and
Security level assignment
27. 27
Authorization levels in a database system can be
set at broad categories as:
Data Level Authorization
Read
Insert
Update
Delete
Schema Level Authorization
Index
Resource
Alter
Drop
28. 28
The syntax for privilege granting is as follows:
GRANT <privilege_list> ON {<table>|<view>}
TO <account_list> [WITH GRANT OPTION]
<privilege_list> is possible data level authorization for
the table or view stated as:
{SELECT | INSERT | UPDATE | DELETE | ALL}
To grant access to a specific column in a table:
GRANT REFERENCES (<column>) ON {<table>|<view>}
TO <account_list> [WITH GRANT OPTION]
29. 29
The syntax for privilege revoking is as follows:
REVOKE <privilege_list> ON {<table>|<view>}
FROM <account_list> [RESTRICT | CASCADE]
To revoke grant option from an account:
REVOKE GRANT OPTION FOR <privilege_list> ON
{<table>|<view>}
FROM <account_list>
30. 30
The syntax to deny a privilege from an account list
is:
DENY <privilege_list> ON {<table>|<view>}
TO <account_list> [CASCADE]
31. 31
Terminologies
Plain text
Cipher text
Key
Encryption
Decryption
P
K
C
encryption
P
P
K
C
decryption
P
32. 32
Cryptography:
rendering plain information unintelligible, and
restoring the encrypted information to intelligible form
Symmetric Key Algorithms
DES (Data Encryption Standard)
IDEA (International Data Encryption Algorithm)
Asymmetric Key Algorithms
RSA (Rivest, Shamir and Adleman)
DSA (Digital Signature Algorithm )
Cryptanalysis : Breaking cipher
33. 33
Authentication is a process of verifying the
identity of a user who is claimed to be.
There are two ways of authenticating a user:
Use of Password.
User Account
Password
Challenge Response
Challenge generated by the server
Encrypted by the user with the private key of the user
Decrypted by the server with the public key of the user