1. MIS CA – 40% Exam – 60% Lecture slides Assignment Test
Taught Courses
Dr N Chaamwe

2. Introduction to Databases
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3. Database systems vs. file-based systems
Examples of DBSs:
Purchases from the supermarket
Purchases using your credit card
Booking a holiday at the travel agents
Using the local library
Taking out insurance
Using the Internet
Studying at university
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4. File-based Systems Collection of application programs that perform
services for the end users (e.g. reports).
Each program defines and manages its own data.
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5. File-based Processing
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6. Limitations of File-based Approach
Separation and isolation of data
Each program maintains its own set of data.
Users of one program may be unaware of potentially useful data held by other programs.
Duplication of data
Same data is held by different programs.
Wasted space and potentially different values and/or different formats for the same item
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7. File structure is defined in the program code.
Data dependence
File structure is defined in the program code.
Incompatible file formats
Programs are written in different languages, and so cannot easily access each others files.
Fixed Queries/Proliferation of application programs
Programs are written to satisfy particular functions.
Any new requirement needs a new program.
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8. Database Approach Arose because: Result
Definition of data was embedded in application programs, rather than being stored separately and independently.
No control over access and manipulation of data beyond that imposed by application programs.
Result
the database and Database Management System (DBMS).
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9. Database various definitions
DB:
Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
System catalog (metadata) provides description of data to enable program–data independence.
Logically related data comprises entities, attributes, and relationships of an organization's information.
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10. DBMS:
A software system that enables users to define, create, and maintain the database and which provides controlled access to this database.
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11. Database Management System (DBMS)
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12. Database languages Data definition language (DDL).
Permits specification of data types, structures and any data constraints. All specifications are stored in the database.
Provides basic data manipulation operations on data held in the database.
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13. Database languages Data manipulation language (DML).
General enquiry facility (query language) of the data.
Procedural DML
allows user to tell system exactly how to manipulate data.
Non-Procedural DML
allows user to state what data is needed rather than how it is to be retrieved.
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14. Database languages Data Control language (DCL).
General administration & security facility (same syntax as query language) used mainly by the DBA.
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15. Views
A view mechanism.
Provides users with only the data they want or need to use.
Allows each user to have his or her own view of the database.
A view is essentially some subset of the database.
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16. Views Benefits include:
Reduce complexity;
Provide a level of security;
Provide a mechanism to customize the appearance of the database;
Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed
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17. Three-level schema architecture
ANSI-SPARC architecture is named after the committee that proposed it, the American National Standard Institute, Standards Planning And Requirements Committee.
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18. Objectives of Three-Level Architecture
• All users should be able to access same data.
• A user's view is immune to changes made in other views.
• Users should not need to know physical database storage details.
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19. Objectives of Three-Level Architecture
DBA should be able to change database storage structures without affecting the users' views.
• Internal structure of database should be unaffected by changes to physical aspects of storage.
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20. Objectives of Three-Level Architecture
DBA should be able to change conceptual structure of database without affecting all users.
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22. The External level
The external level (also known as the user logical level) is the one closest to the users.
It is the level concerned with the way the data is seen by individual users.
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23. The External level
The external schema is used to describe the external level.
It contains a description of a portion of the database that is of concern to the specific user.
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24. The External level
The external view is described in terms of external records, which may be different form the actual stored records.
The view may have a different representation of the same data
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25. The Conceptual level
The level represents the community view of the database as seen by the database administrator.
It is also known as the community logical level or even sometimes just the logical level.
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26. The Conceptual level
The conceptual schema is used to describe what data is stored in the database and the relationships among the data.
The description includes the structure and constraints for the whole database
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27. The Conceptual level
the conceptual schema defines the logical structure of all data in the database.
The conceptual schema is defined by a Data Definition Language (DDL).
There is only one conceptual schema for the database.
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28. The Internal level
It is the description of the implementation of the conceptual schema by means of physical storage structures.
It summarizes how the data are stored on secondary storage devices such as disks and tapes.
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29. The Internal level
However, it is still one level above the actual physical storage, which is usually managed by the operating system.
The internal level does not deal with the physical records but it deals with the internal records (stored records).
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30. The Internal level
Details of how the address space is mapped to physical storage are highly system-specific (e.g. a block or a page)
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33. Logical Data Independence
– Refers to immunity of external schemas to changes in conceptual schema.
– Conceptual schema changes (e.g.
addition/removal of entities).
– Should not require changes to external schema or rewrites of application programs.
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34. Physical Data Independence
– Refers to immunity of conceptual schema to changes in the internal schema.
– Internal schema changes (e.g. using different file organizations, storage structures/devices).
– Should not require change to conceptual or external schemas.
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35. Data Independence
Describes the immunity of the upper levels from the changes in the lower levels
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36. Mappings
The process of transforming requests and results between levels are called mappings.
The three-level architecture involves certain mappings— one conceptual/internal mapping and several external/conceptual mappings.
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37. The conceptual/internal mapping
defines the correspondence between the conceptual view and the stored databases
If a change is made to the storage definition, then the conceptual/internal mapping must be changed accordingly, so that the conceptual schema can remain invariant
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38. The external/conceptual mapping
defines the correspondence between a particular external view and the conceptual view.
If a change is made to the conceptual schema definition, then the External/conceptual mapping must be changed accordingly, so that the External Schema can remain invariant
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39. Functions of a DBMS • A User-Accessible Catalog.
• Data Storage, Retrieval, and Update.
• A User-Accessible Catalog.
• Transaction Support.
• Concurrency Control Services.
• Recovery Services.
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40. Functions of a DBMS • Support for Data Communication.
• Authorization Services.
• Support for Data Communication.
• Integrity Services.
• Services to Promote Data Independence.
• Utility Services.
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41. Roles in the Database Environment
Data Administrator (DA)
Database Administrator (DBA)
Database Designers (Logical and Physical)
Application Programmers End Users (naive and sophisticated)
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42. Advantages of DBMS Control of data redundancy Data consistency
More information from the same amount of data.
Sharing of data
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43. Advantages of DBMS Improved data integrity Improved security
Enforcement of standards
Economy of scale
Improved data accessibility and responsiveness
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44. Advantages of DBMS Balanced conflicting requirements
Increased productivity
Improved maintenance through data independence
Increased concurrency
Improved backup and recovery services
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45. Disadvantages of DBMS Complexity Size Cost of DBMS
Additional hardware costs
Cost of conversion
Performance
Higher impact of a failure
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46. When a DBMS may be unnecessary
If the database and applications are simple, well defined, and not expected to change
If there are stringent real-time requirements that may not be met because of DBMS overhead.
If access to data by multiple users is not required.
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47. Information Resource Dictionary System (IRDS)
Also called as a Data Dictionary or System Catalog
A repository of information (meta-data) describing the data in the database.
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48. Information Resource Dictionary System (IRDS)
It is a tool which enables one to control and manage the information about the data in the design, implementation and expansion phases of a DB
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49. Information Resource Dictionary System (IRDS)
Typically stores:
Names of authorized users.
It is used by modules such as:
Authorization Control.
Integrity Checker.
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50. Information Resource Dictionary System (IRDS)
Who benefits from the use of DDS?
DB administrators
Data administrators
Application personnel
Operating staff
End users
Data auditors.
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51. Lifecycle of Database system development

52. Lifecycle of Database system development
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53. Lifecycle of Database system development
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54. Lifecycle of Database system development
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55. Planning phase
Prior to the first phase of our requirement’s elicitation, a plan must be put forward showing each stage of the life cycle and how it can be performed efficiently and effectively.
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56. System definition phase,
This is where the scope and boundaries of the database application, which includes the major application areas and user groups, are defined.
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57. Requirement collection and analysis Phase
It is concerned with collecting the data and analyzing the user requirements in order to build the database application.
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58. Conceptual model. Create a conceptual schema (High-Level), e..g. ERD
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59. Logical Design
Map conceptual database schema to logical database schema
(Representational), it is also called an Implementation model e.g. Relational
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60. Physical Design
Internal storage structures and file organisations are specified (Physical), e.g. B-tree
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61. The prototype
This is a working model of the database application, which allows the designers or users to visualize and evaluate how the final system will look and function.
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62. Implementation
The phase involves the creation of the external, conceptual and internal definitions and the application programs.
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63. Data Conversion and Loading
If we have a legacy system at this stage, then we need to transfer any existing data into the new database and converting any existing application.
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64. The testing phase
Validating user requirements against the application programs then tests the system. The testing phase aims at executing the application programs with intention to find errors
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65. Operational maintenance
This process involves monitoring & maintaining the system.
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