Database HW 2.0

1.

A) Product

CREATE TABLE Product
(
maker	VARCHAR(255),
model	INT, Primary
type	VARCHAR(255),

)

B) PC

CREATE TABLE PC(
model	INT, PRIMARY KEY
speed	FLOAT,
ram		FLOAT,
hd		FLOAT,
price	INT
);

C) Laptop

CREATE TABLE Laptop(
model	VARCHAR(255),
speed	FLOAT,
ram		FLOAT,
hd		FLOAT,
screen	FLOAT,
price	INT
);

D) Printer

CREATE TABLE Printer(
model	VARCHAR(255),
color	BOOLEAN,
type	VARCHAR(255),
price	INT

);

E)	ALTER TABLE Printer DROP color;

F)	ALTER TABLE Laptop ADD od VARCHAR(255) DEFAULT 'NONE';

2.4.1

A) PROJECTION model (SELECT speed >= 3.00 (PC))

B)  T1 = Product [NATURAL JOIN] Laptop
	PROJECTION maker(SELECT hd >= 100 AND TYPE = 'Laptop' (T))

	or
	PROJECTION (Product [THETA JOIN] Laptop (hd >= 100 AND TYPE = 'Laptop'))

****
C)	T1 = SELECT maker = 'B' (Product)
	PC UNION LAPTOP
	PROJECTION maker, model, price(Product NATURAL JOIN T)

D) PROJECTION model (SELECT type = 'laser' AND color = 'true' (Printer))
E) PROJECTION maker (SELECT type = 'Laptop' AND type != 'PC' (Product))

2.4.2 DRAW

2.4.5 None, they are equal to each other. Please reread the section

2.5.1

A) SELECT speed < 2.00 AND price > 500 (PC) = 0;

B) SELECT screen < 15.4 AND ( hd < 100 or price >= 1000) (Laptop) = 0;