1. Upload Presentations
Using Slideshare
Application
Jennifer Widom

2. The Relational Model
 Used by all major commercial database systems
 Very simple model
 Query with high-level languages: simple yet expressive
 Efficient implementations
Jennifer Widom

3. The Relational Model
Database = structuralfor “unknown” relations in database
Key – attribute of named relations (or tables)
Schema set whose value is unique “undefined”
NULL – – structural description of orin each database
Schemaspecial value description of relations intuple
Each relation has a contents at given point inarecolumns)
Or set of attributes whose combined values (or
Instance –= actual set of named attributes timeunique
Instance actual contents at given point in time
Each tuple (or row) has a value for each attribute
Each attribute has a type (or domain)
Jennifer Widom

4. The Relational Model
Creating relations (tables) in SQL
Create Table Student(ID, name, GPA, photo)
Create Table College
(name string, state char(2), enrollment integer)
Jennifer Widom

5. The Relational Model
 Used by all major commercial database systems
 Very simple model
 Query with high-level languages: simple yet expressive
 Efficient implementations
Jennifer Widom