CS352 Lecture -The Relational Model; Relational Algebra
last revised January 3, 2019 Objectives:
1. To briefly introduce the entity-relationship model 2. To introduce fundamental concepts of the relational model, including terminology, keys, nulls, views 3. To introduce the relational algebra
Materials:
1. Projectable of an ER diagram example 2. Projectable of figure 2.8 from book 3. Projectable/handout of library example database used in class (scheme and instance) 4. Handout of natural language queries against this database 5. Projectable of natural language query processing 6. Projectable of query language classification 7. Projectable of RA queries and updates against example database 8. Projectable of primitive operations equivalent of division
I. Introduction
A.We have seen that a database management system typically describes a database at three levels of description.
1. The physical level - how the data is stored in files
2. The conceptual level - the “big picture”
3. The view level - individual views of the database for each application
B. In order to be able to describe a database, we need some system of notation and representation - a data model. This is true at all levels; but, we are