Introduction to databases
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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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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

  • 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?

Reports l.jpg

  • Expected monthly turnover of renters?

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

Files in sales dept l.jpg
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)

Files in contract dept l.jpg
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

Another example l.jpg
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)

File based processing l.jpg
File Based Processing

File handling routines

Data entry and reports

File definition


Sales application programs

File handling routines

Data entry and reports

File definition


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

Database l.jpg

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

Entity relationship diagram l.jpg
Entity Relationship Diagram













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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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  • “ 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

Slide14 l.jpg

  • 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

Database processing l.jpg
Database Processing

Data entry and reports

Sales application programs



Property, Owner, Renter and Lease details + File Definitions


Data entry and reports

Contracts application programs


Components of dbms environment l.jpg
Components of DBMS environment









Hardware l.jpg

  • 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


Software l.jpg

  • 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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  • 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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  • 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.


  • 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

Advantages of databases l.jpg
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

Disadvantages of databases l.jpg
Disadvantages of Databases

  • Complexity

  • Size

  • Cost of DBMS

  • Additional hardware costs

  • Cost of conversion

  • Performance

  • High impact of a failure