BMGT 402 Lecture Notes - Lecture 2: Conceptual Schema, Relational Model

• School: University of Maryland
• Department: Business and Management
• Course: BMGT 402
• Professor: Woei- Jyh Lee

Document Summary

Ansi-sparc 3-level architecture: external level, conceptual level. External level - user view of database, describes the relevant part of the database. Conceptual level - community view, describes what data is stored in the database and relationships in the data. Internal level - how data is stored in the database. Changing something on bottom (internal) will not affect what is above it. Changing something in external or conceptual level will affect the bottom levels. struct staff { int staffno; int branchno; char fname [15]; first 15 characters of first name char lname [15]; first 15 characters of last name. Conceptual schema is different because it brings together the external views and begins to create logical relationships. Internal schema is different because it is the code, the last step before ready to create database. Changing the lower level internal schema does not affect the middle or upper level (conceptual and external schemas) Internal schema level: conceptual/internal mapping and physical data independence.