Computer lecture (1) m.nasir
- 1. Database System Today we will learn: Some common uses of database systems The characteristics of file-based systems The problem with the file-based approach The meaning of the term ‘Database’ The meaning of the term Database Management System’ (DBMS) The typical functions of DBMS The major components of the DBMS environment The advantages and disadvantages of DBMSs
- 3. Database Systems Purchase from the U-mart Cash withdrawal from ATM (of The Bank of Punjab, Fowara Chowk, Gujrat) Purchase using your credit card Registration at NADRA office Using the internet University of Gujrat Information System (UOGIS)
- 4. Database Systems A collection of programs that perform services for the end-user.
- 6. Database Systems The Limitations of the file-based approach Separation and isolation of data Duplicate of data Data dependence Incompatible file formats
- 7. Database Systems Fine Books Issued Father Name Name Reg_Number Library Grade Semester Class Address Name Reg_Number Examination Class Address Phone Father Name Name Reg_Number Registration
- 8. Database Systems -A software system that enables users to define, create, and maintain the database and that provides controlled access to this database. A database management system (DBMS) is computer software that manages databases. Examples: Oracle, SQL Server, Informix, Sybase, Ingress
- 9. Database Systems DBMS Database containing centralized shared data Application #1 Application #2 Application #3
- 10. Database Systems -Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
- 11. Database Systems Shared collection – can be used simultaneously by many departments and users. Logically related - comprises the important objects and the relationships between these objects. Description of the data – the system catalog (meta-data) provides description of data.
- 12. Database Systems Database A collection of related files ^ File A collection of records about a particular set of people, objects, entities and so on ^ Record A collection of related fields associated with a single person, object, entity and so on ^ Field A collection of bytes representing a single attribute. ^ Byte A collection of bits representing a single character ^ Bit A binary digit
- 13. Database Systems A database is a collection of integrated files. Integrated : Collection of files. Note: A FILE is a collection of logical records in a tabular format. A RECORD contains fields (or attributes ) about the entity. A field is same as an ‘attribute’
- 14. Advantages of Database Approach RegistrationExamination Library Applications Library Examination Applications Registration Applications Database Management System University Students Database - Data Sharing - Data Independence - Controlled Redundancy - Better Data Integrity
- 15. Database Systems Data Sharing Data Independence Controlled Redundancy Better data Integrity Data consistency Better data security Faster development of new applications Economy of scale Better concurrency Better backup procedures
- 16. Database Systems Higher costs (DBMS) Conversion cost (manual to computerized ) More difficult recovery
- 17. Database System Today we will learn: •Database Users •Typical Components of Database Environment •Data Independence •3-Level Architecture
- 18. Application Programmers End Users Naïve Sophisticated Instructor: Ikram. Database Systems. CS-212
- 19. DatabaseAdministrator (DBA) A person who has central control over data and programs that access this data Instructor: Ikram. Database Systems. CS-212
- 20. Functions of DBA Create Database Creating Users Granting Roles & Privileges Routine Maintenance Backups Monitoring disk space Monitoring jobs running Instructor: Ikram. Database Systems. CS-212
- 21. Database DBMS “How” to get Application Programs “What” to get End users interact Application Programmers Database Administrators Database Designers develop maintain design Software Users Data
- 22. Each user should be able to access the same data, but have a different customized view of data. Each user should be able to change the way he or she views the data, and this change should not affect other users. User should not have to deal directly with physical database storage details. The internal structure of the database should be unaffected by the changes to the physical aspects of storage, such as change over to a new storage devices.
- 23. External Level Conceptual / Logical Level Internal Level Physical Data Organization View 1 View 2 View n Conceptual Schema Internal Schema Database User 1 User 2 User n Ext/Con Mapping Con/Int Mapping 3-Level Architecture
- 24. This Level Describes-The Part of Database that is relevant to each user e.g. Registration,Accounts etc Calculated Data:That is not actually stored in the database but is created when needed e.g. age DBMS uses external views to create users interface for different users which is both the facility and barrier. External Schema are evolves as user needs are modified over time
- 25. First Name: Rana Last Name: Aslam Date of Birth: 12 Sep, 1970 Name: R. Aslam Age: 24y,10d Dept: Sales Saleem Saleema Corresponds to different views of Data External Level
- 26. Entire information structure of the database. Also called “The Community view of data” All entities, attributes and their relationships are represented. Representing data and constraints on data Contains information about the security and integrity information Relatively constant: designed with the present as well as future needs of an organization.
- 27. Name DoB DepId Rana Aslam 12/09/70 D001 Marya Wasti 29/02/80 D005 First Name: Rana Last Name: Aslam Date of Birth: 12 Sep, 1970 Name: R. Aslam Age: 24y,10d Dept: Sales Saleem Saleema Conceptual / Logical View Describes all entities their attributes their relationships with constraints
- 28. Although these are at same level but PhysicalView ▪ Actual Data (on the disk) binary format. ▪ Use OS to store the Data InternalView ▪ Internal Record: a single stored record ▪ Does not just contain what we see at the conceptual level
- 29. Name DoB Deps DepId Rana Aslam 12/09/70 5 D001 Marya Wasti 29/02/80 0 D005 First Name: Rana Last Name: Aslam Date of Birth: 12 Sep, 1970 Name: R. Aslam Age: 24y,10d Dept: Sales Saleem Saleema 01110011010011100101001010100101010010101….. BH RH Rana Aslam 120970 5 D001 RH Marya Wasti… Contains stored Data (Record) Internal View
- 30. External / Conceptual mapping (correspondence between external level and conceptual level) Conceptual / Internal (correspondence between and conceptual level and internal level)
- 31. Specifies mapping between objects in the external view to those in the logical model External to logical model
- 32. Specifies mapping between objects in the logical model to those in the physical model- data independence Logical to Physical
- 34. Very Important Feature Data independence is major most outcome of 3-L Arch The immunity of applications to change in storage structure and access strategy
- 35. Changes in lower level do not affect the upper levels Mind the direction please
- 36. Logical Data Independence Physical Data Independence
- 37. Changes in conceptual model do not affect the external views Immunity of external level from changes at conceptual level
- 38. Adding a new file etc. Adding a new field in a file Changing type/size Deleting an attribute
- 39. Changes in the internal model do not affect the conceptual model Immunity of Conceptual level from changes at Internal level
- 40. Entity (an object) Attribute (characteristics of object) Constraints (limit, check, control)