n-ary operations
From: ruben safir <ruben_at_mrbrklyn.com>
Date: Thu, 11 Dec 2014 11:15:12 -0500
Message-ID: <m6cfua$m8i$1_at_reader1.panix.com>
I have this quote fro a textbook
relation (set). In general, the result of R(A1, A2, ..., An) × S(B1, B2, ..., Bm) is a relation
Q with degree n + m attributes Q(A1, A2, ..., An, B1, B2, ..., Bm), in that order.
The resulting relation Q has one tuple for each combination of tuples—one from R
and one from S. Hence, if R has nR tuples (denoted as |R| = nR), and S has nS tuples,
then R × S will have nR * nS tuples.
The n-ary CARTESIAN PRODUCT operation is an extension of the above concept, which produces new tuples by concatenating all possible combinations of tuples
from n underlying relations.
Date: Thu, 11 Dec 2014 11:15:12 -0500
Message-ID: <m6cfua$m8i$1_at_reader1.panix.com>
I have this quote fro a textbook
6.2.2 The CARTESIAN PRODUCT (CROSS PRODUCT)
Operation
Next, we discuss the CARTESIAN PRODUCT operation—also known as CROSS
PRODUCT or CROSS JOIN—which is denoted by ×. This is also a binary set
opera-
tion, but the relations on which it is applied do not have to be union
compatible. In
its binary form, this set operation produces a new element by combining
every
relation (set). In general, the result of R(A1, A2, ..., An) × S(B1, B2, ..., Bm) is a relation
Q with degree n + m attributes Q(A1, A2, ..., An, B1, B2, ..., Bm), in that order.
The resulting relation Q has one tuple for each combination of tuples—one from R
and one from S. Hence, if R has nR tuples (denoted as |R| = nR), and S has nS tuples,
then R × S will have nR * nS tuples.
The n-ary CARTESIAN PRODUCT operation is an extension of the above concept, which produces new tuples by concatenating all possible combinations of tuples
from n underlying relations.
What is an n-ary operation? I see this repeadely but I am not understanding its meaning.
Ruben Received on Thu Dec 11 2014 - 17:15:12 CET