Query Languages and the Relational Algebra - Access Database Design and Programming - page 52

gain here will prove very useful. I should also mention that Access SQL is more powerful
than the Access Query Design interface, so some operations must be written directly in
SQL. Fortunately, Access allows the user to write SQL statements.

Let us recall some notation used earlier in the topic. In order to emphasize the attributes
of a table (or table scheme), we use the notation T(A 1 ,...,A n ). As an example, the BOOKS
table can be written:

BOOKS(ISBN,Title,PubID,Price)

and the Books table scheme can be written:

Books (ISBN,Title,PubID,Price)

5.3.1 Renaming

Renaming refers simply to changing the name of an attribute of a table. If a table T has an
attribute named A, we will denote the table resulting from the operation of renaming A to
B by:

ren A

B (T)

For Table 5-5:

Table 5- 5 . The BOOKS table with origin a l fields

ISBN Title Price PubID

0 -103-45678-9 The Firm $24.95 1

0-11-345678-9 Moby-Dick $49.00 2

0 -12-333433-3 War and Peace $25.00 1

the result of performing:

is shown in Table 5-6.

Table 5- 6 . The BOOKS table with renam e d fields

BookID Title Cost PubID

0 -103-45678-9 The Firm $24.95 1

0-11-345678-9 Moby-Dick $49.00 2

0 -12-333433-3 War and Peace $25.00 1