L02 - Database Basics

L02 - Database Basics - Database System Structures and...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Database System Structures and Components Database System Structures and Components ¡ Database systems can be viewed from three levels of abstraction: ¢ physical level ¢ conceptual/logical level ¢ external/user/view level ¡ Database System Components ¢ the front end, the middle levels, and the back end ¡ Database Users ¢ classified into five distinct categories Levels of Abstraction Levels of Abstraction ¡ Physical level: describes how a record (e.g., customer or student) is stored. ¡ Conceptual/Logical level: describes data stored in database, and the relationships among the data. type student = record student_id : string; student_name : string; student _major : string; student_gpa: double; end ; ¡ View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes. Layers of Abstraction (i) Layers of Abstraction (i) ¡ Abstraction from physical to conceptual/logical makes sense ¢ the record structure translates directly to a storage structure ¢ BUT … we don’t want the application programs to depend on the low level details of the storage structure ¢ Abstracting the physical level provides physical data independence Layers of Abstraction (ii) Layers of Abstraction (ii) ¡ Abstraction to the external perhaps needs a little motivation ¢ Suppose that the Clarkson Provost has a database that has a table with three columns – ¢ One day he’s looking at this and he realizes this is not so smart ¡ he’s wasting a lot of space ¡ it’s hard to update – suppose that the chair of a department changes Faculty Dept Chair Conry Hou C Lynch Matthews Peploski … ECE ECE MCS MCS Chem … Ortmeyer Ortmeyer Turner Turner Christiansen … Layers of Abstraction (iii) Layers of Abstraction (iii) Faculty Dept Conry Hou C Lynch Matthews...
View Full Document

This note was uploaded on 04/08/2008 for the course EE 468 taught by Professor Conry during the Spring '08 term at Clarkson University .

Page1 / 16

L02 - Database Basics - Database System Structures and...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online