I'm in a databases class and this homework is due next week. I have been home sick for a couple days so I can't go to class to ask this question right now and I'd hate to waste time, so hopefully someone can help me out on here.
I'm a little confused, this is problem #1:
Problem1 [15′ = 5′ ∗ 3]
Given the following relations $R$ and $S$, where $R(A,B,C) =((x,y,z); (j,g,s);(y,x,g); (q,w,e))$ and $S(B,C,D) = ((g,s,r); (y,x,g); (r,q,e))$ compute the following operations:
Cartesian product: $R\times $S;
Natural join: $R \bowtie S$;
Equal join: $R \bowtie R.B=S.B S$
First: Is there a significance to the [15' = 5' * 3] next to the problem number? each problem has something like that and I'm not sure what's going on or if my teach is being silly.
Second: What is with the $(A,B,C)$ behind $R$? does it relate to the sets on the right side of the equal sign? I took discrete math and I feel confident I can do this work easily enough, but I have a feeling I'm missing out on some key concepts.
If I'm totally wasting time and it'd be too much to try to explain, could someone point me in the direction of a solid tutorial that can explain how this format works? I've been reading the textbook diligently, but the lectures haven't been following the book content very closely it seems.
The notation is a bit non-standard, so let me try to formulate it in a more standard way. We have four sets $A, B, C, D$, and two relations $R$ and $S$. $R$ is a relation on $A \times B \times C$ and $S$ is a relation on $B \times C \times D$. We are then told that $R$ and $S$ are given as follows.
$$R = \{(x,y,z),(j,g,s),(y,x,g),(q,w,e)\}$$ $$S = \{(g,s,r),(y,x,g),(r,q,e)\}$$
Next we are told to find the
Cartesian product of $R$ and $S$,
natural join of $R$ and $S$,
equal join of $R$ and $S$.
Do you know how to do 1-3?