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Introduction to Databases PowerPoint PPT Presentation


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Introduction to Databases. Case Example: File based Processing. Real Estate Agent’s office Property for sale or rent Potential Buyer/renter Staff/employees. Queries. 3-bed room apts for sales? Flats within 3 miles of the city? Average price of house? Average rent for 2 BR flat?

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Introduction to Databases

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Introduction to databases l.jpg

Introduction to Databases


Case example file based processing l.jpg

Case Example: File based Processing

  • Real Estate Agent’s office

  • Property for sale or rent

  • Potential Buyer/renter

  • Staff/employees


Queries l.jpg

Queries

  • 3-bed room apts for sales?

  • Flats within 3 miles of the city?

  • Average price of house?

  • Average rent for 2 BR flat?

  • Total annual salary for staff?


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Reports

  • Expected monthly turnover of renters?

  • This month’s turnover compare to the last month?


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Files in Sales Dept

Selling and renting of properties

  • Property_for_rent (Pno, Street, Area, City, Pcode, Type, Rooms, Rent, Ono)

  • Owner (Ono, Fname, Lname, Address, Tel_no, Pref_Type, Max_rent)

    Potential renters

    Renter (Rno, Fname, Lname, Address, Tel_No, Pref_Type, Max_rent)


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Files in Contract Dept

  • Lease(Lno, Pno, Rent, Payment, Deposit, paid, Start, Finish, Duration)

  • Property_for_rent (Pno, Street, Area, City, Pcode, Rent)

  • Renter (Rno, Fname, Lname, Address, Tel_No)

  • Data entry

  • File maintenance

  • Reports generation


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Another example

Payroll Dept

Staff_salary(Staff No, First Name, Last Name, Address, Date_of_Birth, Salary, National Insurance Number, Branch Number)

Personnel Dept:

Staff(Staff No, First Name, Last Name, Address, Telephone Number, Position, Date_of_Birth, Salary, National Insurance Number, Branch Number)


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File Based Processing

File handling routines

Data entry and reports

File definition

Sales

Sales application programs

File handling routines

Data entry and reports

File definition

Contracts

Contracts application programs


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Limitations of File-Based Processing

  • Separation and Isolation of data

  • Duplication of data

  • Data dependence

  • Incompatibility of files

  • Fixed queries/ proliferation of application programs


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Database

  • “A shared collection of logically related data (and a description of this data) designed to meet the information needs of an organization.”


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Entity Relationship Diagram

Staff

IsAllocated

Oversees

Property_for_Rent

Has

Branch

Viewing

Takes

Requests

Owns

Owner

Renter


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Parts of ER diagram

  • Six entities (the rectangles): Branch, Staff, Property_for_Rent, Owner, Renter and Viewing.

  • Six relationships (the diamonds): IsAllocated, Has, Overseas, Owns, Requests, and Takes


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DBMS

  • “ A software system that enables users to define, create and maintain the database and provides controlled access to this database.”

  • Data definition Language (DDL): data types, structures and constraints on the data.

  • Data Manipulation Language (DML): insert, update, delete, and retrieve data

  • Query Language: general enquiry facility


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  • Two types of DML:

    • Procedural: manipulates the database record by record.

    • Non-Procedural: operates on a set of records.

      • Most common is Structured Query Language (SQL)

  • Controlled Access to the database:

    • security system

    • integrity system

    • Concurrency controlled, shared access

    • recovery control system

    • user accessible catalog


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Database Processing

Data entry and reports

Sales application programs

Sales

DBMS

Property, Owner, Renter and Lease details + File Definitions

Database

Data entry and reports

Contracts application programs

Contracts


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Components of DBMS environment

Data

Hardware

Software

Procedures

People

Machine

Bridge

Human


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Hardware

  • Some DBMS run only on particular hardware and operating systems

  • Minimum amount of main memory and disk space to run

  • Client -Server architecture:

    • Central computer runs the backend of the DBMS

    • Other computers run the frontend


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Dream Home hardware configuration

Northern Office

Western Office

Database server

Eastern Office

Southern Office

Database


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Software

  • The DBMS software

  • Application programs: C, COBOL, Fortran, Ada etc.

  • Using a fourth level language such as SQL

  • Fourth generation tools:

    • rapid development of applications

    • non-procedural query languages

    • report generators

    • form generators

    • graphic generators

    • application generators

  • Fourth generation tools can improve productivity.


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Data

  • The structure of the database is called the schema.

  • Tables: Property_for_Rent, Owner, Renter and Lease

  • Attributes

  • System Catalog contains:

    • Names, types, and sizes of data items

    • Integrity constraints on data

    • Names of authorized users who have access to the data

    • What indexes and storage structures are being used- Tree structures.


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Procedures:

  • Log on to the DBMS

  • Use particular DBMS facility or application program

  • Start and stop the DBMS

  • Make backup copies of the database

  • Handle hardware and software failures

  • Change the structure of the table, reorganize the data across multiple disks, improve performance, or archive data to secondary storage.

    PEOPLE:

  • DB engineers, DB designers, DB developers/ programmers


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Data and database administrators

  • Data Administrator (DA)

    • management of data (database planning, development, maintenance of standards, policies, procedures and conceptual and logical database design).

  • Database Administrators:

    • Physical database design and implementation, security and integrity control, maintanence of the operational system and ensuring satisfactory performance for the applications and users.


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Database designers

  • Logical database designers:

    • Entities, attributes, relationships, constraints Business rules

  • Physical database designers:

    • Decides how it is to be physically realized.


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Application Programmers

  • Retrieving, inserting, updating and deleting

  • Programs

    • Third Generation Language (3GL)

    • Fourth Generation Language (4GL)

  • End Users:

    • Inexperienced Users

    • Sophisticated users


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The Paradigm Shift

  • The structure of the database is determined using the database design.

  • Paradigm shift: think of the data first and the application later.

  • Poorly designed database --> errors

  • Well designed database --> correct information

  • A complete methodology for database design.

    • Entity- Relationship diagram

    • Guidelines to help identify the entities, attributes and relationships


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Advantages of Databases

  • Control of data redundancy

  • Data consistency

  • More information from the same amount of data

  • Sharing the data

  • Improve data integrity and improve security

  • Enforce standards

  • Economies of scale

  • Balance the conflicting requirements

  • Improve data accessibility and responsiveness

  • Increase productivity

  • Improve maintenance through data interdependencies (pgm-data independence)

  • Increase concurrency

  • Improve backend recovery services


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Disadvantages of Databases

  • Complexity

  • Size

  • Cost of DBMS

  • Additional hardware costs

  • Cost of conversion

  • Performance

  • High impact of a failure


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