Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
DBMS
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Management System
(DBMS)
• Collection...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Purpose of Database System• In the early days,...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Purpose of Database Systems (Cont.)• Drawbacks...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
5© Pearson Education ...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
• External Level
– Us...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
• Internal Level
– Ph...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence
• Logical Data Independence
...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence
• Physical Data Independence...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence and the Three-
Level Archite...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Languages
• Data Definition Language ...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Languages
• Data Manipulation Languag...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Entity-Relationship Model
Example of schema in...
Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
• An ER model is an abstract way to describe a...
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Comp107 chep6

  1. 1. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING DBMS
  2. 2. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Database Management System (DBMS) • Collection of interrelated data • Set of programs to access the data • DBMS contains information about a particular enterprise • DBMS provides an environment that is both convenient and efficient to use. • Database Applications: – Banking: all transactions – Airlines: reservations, schedules – Universities: registration, grades – Sales: customers, products, purchases – Manufacturing: production, inventory, orders, supply chain – Human resources: employee records, salaries, tax deductions • Databases touch all aspects of our lives D.Balaganesh LINCOLN UNIVERSITY COLLGE 2
  3. 3. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Purpose of Database System• In the early days, database applications were built on top of file systems • Drawbacks of using file systems to store data: – Data redundancy and inconsistency • Multiple file formats, duplication of information in different files – Difficulty in accessing data • Need to write a new program to carry out each new task – Data isolation — multiple files and formats – Integrity problems • Integrity constraints (e.g. account balance > 0) become part of program code • Hard to add new constraints or change existing ones D.Balaganesh LINCOLN UNIVERSITY COLLGE 3
  4. 4. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Purpose of Database Systems (Cont.)• Drawbacks of using file systems (cont.) – Atomicity of updates • Failures may leave database in an inconsistent state with partial updates carried out • E.g. transfer of funds from one account to another should either complete or not happen at all – Concurrent access by multiple users • Concurrent accessed needed for performance • Uncontrolled concurrent accesses can lead to inconsistencies – E.g. two people reading a balance and updating it at the same time – Security problems • Database systems offer solutions to all the above problems D.Balaganesh LINCOLN UNIVERSITY COLLGE 4
  5. 5. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Three-Level Architecture 5© Pearson Education Limited 1995, 2005
  6. 6. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Three-Level Architecture • External Level – Users’ view of the database. – Describes that part of database that is relevant to a particular user. • Conceptual Level – Community view of the database. – Describes what data is stored in database and relationships among the data. 6
  7. 7. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Three-Level Architecture • Internal Level – Physical representation of the database on the computer. – Describes how the data is stored in the database. 7
  8. 8. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Data Independence • 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. 8
  9. 9. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Data Independence • 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. 9
  10. 10. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Data Independence and the Three- Level Architecture 10© Pearson Education Limited 1995, 2005
  11. 11. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Database Languages • Data Definition Language (DDL) – Allows the DBA or user to describe and name entities, attributes, and relationships required for the application – plus any associated integrity and security constraints. 11© Pearson Education Limited 1995, 2005
  12. 12. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Database Languages • Data Manipulation Language (DML) – Provides basic data manipulation operations on data held in the database. • Procedural DML – allows user to tell system exactly how to manipulate data. TCL transmission Control Language 12
  13. 13. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING Entity-Relationship Model Example of schema in the entity-relationship model D.Balaganesh LINCOLN UNIVERSITY COLLGE 13
  14. 14. Subject Name Code Credit Hours FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING • An ER model is an abstract way to describe a database. Describing a database usually starts with a relational database, which stores data in tables. Some of the data in these tables point to data in other tables - for instance, your entry in the database could point to several entries for each of the phone numbers that are yours. The ER model would say that you are an entity, and each phone number is an entity, and the relationship between you and the phone numbers is 'has a phone number'. Diagrams created to design these entities and relationships are called entity– relationship diagrams or ER diagrams
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