DBMS, April 1998

SQL Revision

I think there may be a typo in the November 1997 "SQL for Smarties," by Joe Celko. In the section "Constraints and Denormalization," it states:

CREATE TABLE Advisors(teacher CHAR(15) NOT NULL,dept CHAR(15) NOT NULL,PRIMARY KEY (advisor, dept));

CREATE TABLE Advisors(teacher CHAR(15) NOT NULL,dept CHAR(15) NOT  NULL,PRIMARY KEY (teacher, dept));

David Eyre
David.Eyre@HammondSuddards.co.uk

You are correct; I had a typo in the table declaration. Thanks for the correction. ýJoe Celko

Query Correction

I read with interest Ralph Kimballýs February DBMS column "Human Resources Data Marts." I have a question regarding how the design enables the "second query" outlined in the system requirements. On page 19, paragraph 3, it states that "You can make a time-based cut through the employee data-base by choosing a specific date and time and constraining this date and time to be equal to the transaction date/time and less than the transaction end date/time." I am unclear about the use of the word "equal," which seems to imply that a transaction record must exist for the precise date/time youýre investigating. Should this read "greater than or equal to?" If so, phew, I understand. If not, what am I missing?

Diane Stevens
dstevens@mfs.com

Thanks for pointing out the typo. Youýre right, it should be "greater than or equal to." ýRalph Kimball

Firewall Additions

I believe that Marcia Gulesianýs eclectic article "JDBC and Firewalls" (DBMS, February 1998) illuminates its complex subject matter in ways that should prove extremely helpful to both managers and system developers alike. At the same time, I want to comment that nowhere does your account of security, performance, and cost mention the JDBC drivers from, perhaps, the most significant database vendor, Oracle. Iýd be interested to learn why it was not included in your otherwise thorough presentation. Iýd also appreciate any information that you can give me on the compatibility between Oracleýs nascent JDBC products and the market-leading firewalls.

Paul Brusil, Ph.D.
brusil@snad.ncsl.nist.gov

The JDBC drivers from Oracle that were available when my article went to press and, before that, when I was developing applications with the JDBC products that were the subjects of my article, consisted of beta code. Since then, fully supported versions have shipped for Oracle7 and 8. (Not to mention the Oracle Lite ORDBMS 3.0 JDBC driver, now bundled with Oracleýs new desktop product.) Today, both the Oracle JDBC/OCI and thin JDBC drivers can be used with most firewalls that have been SQL*Net certified. These include the following:

• Stateful inspection firewalls: firewalls from Checkpoint, SunSoft, and CISCO Systems
• Proxy-based firewalls: firewalls from Raptor, Milkyway Networks, Trusted Information Systems, Secure Computing Corp., and Global Internet.

Data Mart Insight

I just read Ralph Kimballýs article "Bringing Up Supermarts" in the January 1998 edition of DBMS. We are just embarking on a data mart project and are facing all the issues he discusses with newfound clarity. I couldnýt have scripted a better source from which to gain information. Thanks for a great read and for the insight.

Ian Fisher
H.A. Simons Ltd.
ifisher@hasimons.com