CISC 332 Lecture Notes - Lecture 3: Database Design, Physical Data Model, Logical Data Model

• School: Queen's University
• Department: Computing
• Course: CISC 332
• Professor: Wendy Powley

Document Summary

Physical level - storage information such as file organization and indexes. Logical level - data described in terms of the dbms model. External level - views allow data to be customized to users or groups of users. Data independence - application programs are insulated from changes in the way the data is structures and stored. If logical structure changes; views can be adjusted to maintain the structure originally seen by the user - logical data independence. If the physical storage changes, the logical level maintains the :structure: of the data - physical data independence. Schema - the logical structure of the database. Example: the database consists of information about a set of customers and accounts and the relationship between them. Analogous to type information of a variable in a program. Physical schema: database design at the physical level. Logical schema: database design at the logical level. This model is good for sketching out the plan and showing relationships.