Re: SQR-USERS Digest - 17 Jul 1999 to 19 Jul 1999

[Krisjanis Gale <Krisjanis.Gale@NY.FRB.ORG>]

no newbie programmer camp.
i wouldn't even wish that for my worst enemies =)
(ah, not-so-fond memories of CS111.)

cross product is a cross-tab, yes.
the prof. i had for Database Systems I insisted on using
algebraic terminology for all his explanations of data set theory.
he even had us wade through tuple calculus.  (YUCK!)
in tuple calculus, a simple select is known as a "projection"
(denoted with Pi), and selecting across two tables is
a "cross product" (denoted by an 'x') and renaming a table
requires use of a function denoted by Rho.

for example, this select:

  select e.employee_name, i.employee_id
  from employee e, identification i

would look like this:

Pi ( e.employee_name, i.employee_id ) ( Rho ( employee e ) x Rho ( identification i ) )

ugly, huh?
gosh did i ever despise that class.

(kris)janis p. gale
hrsd - federal reserve bank of new york
x8163

>>> Anne-Marie Matula <amatula@OIT.UMASS.EDU> Tuesday, July 20, 1999 9:59:22 AM >>>
>Krisjanis Gale <Krisjanis.Gale@NY.FRB.ORG> wrote:

>so i modified it by simply doing a cross-product
>of dba_tables and dba_tab_columns
>and did a select distinct / order by table_name.
>and then it only ran for about a half hour.

What exactly is a cross-product? A cross-tabular select?  I just never heard
the term used...I hope admitting that doesn't boot me back down to newbie
programmer camp!

Have a great day!
Anne-Marie

P.S. I agree "SQR in PeopleSoft and other applications" is excellent! It has
a great section on optimizing SQL statements. I don't recall any other books
that had such a concise summary of that!

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Anne-Marie Matula
Student Information System Project
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