Howdi,

I'm not asking for the answer - but a gentle nudge in the right direction

I've been asked to write a Relational Algebra Expression to get the most
expesive item

i'm not really sure how to go about it,

any help appreciated

"riley" <k@r.net.au> wrote

What are the properties of the most expensive item?

riley wrote:
Hint: First write an algebra expression for the items that are *not* the
most expensive. Then use this expression to build a bigger expression that
computes the answer that you want.

In case you have trouble finding that particular expression let me remind
you of the following trivial truth:

An item is not the most expensive one if there is another one that is more
expensive.

Good luck,

-- Jan Hidders

thank you for advice so far,

Find the "not most expensive items" sure -I get how I could do this with a
loop...like java, but in Relational Algebra?

And How can I traverse down a column comparing the next row to the previous?

the question says


Do I make a recursive loop or something?

as I don't know how many items there are I can't see how I can, just using
">" and "<" make sure I definately have a group of either the most
expensive, or not the most expensive item..

(this question is actually really easy and I'm missing something simple,
yeh?)

riley

"Jan Hidders" <jan.hidders (AT) pandora (DOT) be> wrote

"Riza" <k (AT) wa (DOT) bp.net> wrote

Yeh. You want to write a single expression that involves no looping or
recursion. Just describe what you want or what you don't want.