Реляционная алгебра. Тема 3.2

1.

:

2.

:

3.

4.

5.

6.

7.

Dn
<d1,d1,...dn
-
.
R

8.

-

9.

10.

Drivers
COMPANY
DRIVER

11.

COMPANY
DRIVER

12.

-

13.

14.

8

15.

ID
NAME
COMPANY
PRICE
123
190
156
60
235
100
623
130

16.

Sellers

17.

18.

.
ID
PRICE
123
190
156
60
235
100
623
130

19.

20.

90.
ID
NAME
COMPANY
PRICE
123
190
23
5
100
62
3
130

21.

:
ID
NAME
COMPANY
PRICE
123
190
235
100

22.

(PRICE<100 ) PRODUCTS
COMPANY

23.

24.

:
PRODUCTS × SELLERS
PRODUCTS.ID
NAME
COMPANY
PRICE
SELLERS.ID
123
190
123
156
60
156
123
190
156
156
60
123
SELLER

25.

PRODUCTS × SELLERS
SELLER

26.

ID

27.

PRODUCTS.ID
NAME
COMPANY
PRICE
SELLERS.I
D
123
190
123
156
60
156
235
100
235
623
130
623
SELLER

28.

PRODUCTS ⋈ SELLERS
PRODUCTS.I
D
NAME
COMPANY
PRICE
SELLER
123
190
OOO
156
60
235
100
623
130

29.

30.