The database scheme consists of four tables:
Product (maker, model, type)
PC (code, model, speed, ram, hd, cd, price)
Laptop (code, model, speed, ram, hd, screen, price)
Printer (code, model, color, type, price)
The Product table contains data:
- maker
- model number
- type of product ('PC', 'Laptop', or 'Printer').
It is assumed that model numbers in the Product table are unique for all makers and product types.
Each personal computer in the PC table is unambiguously identified by:
- unique code
- additionally characterized by its model (foreign key referring to the Product table)
- processor speed (in MHz) – speed field
- RAM capacity (in Mb) - ram
- hard disk drive capacity (in Gb) – hd
- CD-ROM speed (e.g, '4x') - cd
- price.
The Laptop table is similar to the PC table, except that instead of the CD-ROM speed, it contains the screen size (in inches) – screen.
For each printer model in the Printer table, its output type (‘y’ for color and ‘n’ for monochrome) – color field, printing technology ('Laser', 'Jet', or 'Matrix') – type, and price are specified.
Sourse: https://www.sql-ex.ru/
Database Schema: https://www.sql-ex.ru/help/select13.php#db_1