Wonderfully rich reply - thanks.

But I think, maybe, some miscommunications.

To put it into similar terms:

• I have companies (ex: ABC Inc, XYZ Inc, ...) and I have product classes (ex: pens, liquid nitrogen, desk chairs, fork lifts, plywood, fourier-transform-infrared-spectrometres,...)

• yes, one of the attributes of a company is its size_factor

• a product_class has no attributes

• Someone has canvassed ~30,000 companies and asked them:
  • do you belong to industry group X (ex: more than X employees)?
  • do you belong to industry group Y (ex: located in Ontario, California)?
  • do you belong to industry group Z(ex: less than 5 years in business)?
  • do you use product class A?
  • do you use product class B?
  • do you use product class C?
  • ...and so on, for ~12,000 product classes.

So, all the info could have been put into one big 30,000 row x 12,000 column table, and then just query

SELECT company WHERE (group_a = 1 and product_class_C  = 1);
[download]

But I still have to repeat that query for 350 combinations of group and product_class.

Originally, there was only going to be a requirement to produce a half-dozen cross-references at a time. So, came the idea of the reverse-index tables - easy and quick to identify the ten tables needed, find the intersection of these little <= 10Kb tables that are often only a few hundred rows long, and sum the size-factors.

But THEN someone said "Hey, that's great - and fast - here, do that for this report of 350 intersections."

Update: I appear to have at least partially answered my own question - even if it was done the other way, there'd still be 350 queries to run, except each one on a full 30k-row x 12k column table!

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.