MESSAGE
| DATE | 2014-12-11 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [LIU Comp Sci] Fwd: Re: Database Class concepts which are still unclear
|
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Date: Thu, 11 Dec 2014 14:38:27 -0500
From: Ruben Safir
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Date: Thu, 11 Dec 2014 14:30:41 -0500
Message-ID:
Subject: Re: Database Class concepts which are still unclear
From: Ping-Tsai Chung
To: Ruben Safir
Cc: Ping-Tsai Chung
Content-Type: multipart/alternative; boundary=f46d04428270d07cfd0509f5cfd6
->What is an n-ary operation? It is mentioned several times, but I don't
see an answer
*n-ary operation is *
*Z1(A1, A2, ..., An) X Z2(A1, A2, ..., An) X ..... X Zn(A1, A2, ..., An)*
The n-ary CARTESIAN PRODUCT operation is an extension of the of CARTESIAN
PRODUCT operation—also known as CROSS
PRODUCT or CROSS JOIN—which is denoted by ×. This is also a binary set
operation, which produces new tuples by concatenating all possible
combinations of
tuples
On Thu, Dec 11, 2014 at 11:03 AM, Ruben Safir wrote:
> 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
> member (tuple) from one relation (set) with every member (tuple) from
> the other
> relation (set). In general, the result of R(A1, A2, ..., An) × S(B1, B2,
> ..., Bm) is a rela-
> tion 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? It is mentioned several times, but I don't
> see an answer
>
> Ruben
>
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