Example: University Database
A Conceptual schema:
- Students(sid: string, name: string, login: string,
age: integer, gpa:real)
- Courses(cid: string, cname:string, credits:integer)
- Enrolled(sid:string, cid:string, grade:string)
A possible Physical Schema:
- Relations stored as unordered files.
- Index on first column of Students.
An External Schema (View):
- Course_info(cid:string,enrollment:integer)