Ted Holt
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Guru: SQL Can Read Program-described Data
September 21, 2020 Ted Holt
I thought I left program-described database files behind me in 1988. That’s when I left my last S/36 shop to begin working on the S/38. Well, I did, but not completely. From time to time I work on a system with program-described files, and even some externally described files have program-described fields. Fortunately — and I owe this to Scott Forstie — I have learned that SQL can read program-described data. Will wonders never cease?
You may be thinking, “This article doesn’t apply to me. Our files are externally described.” You may be right. Then again, you may be wrong. …
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Guru: Qualified Files – Underused and Unappreciated
September 14, 2020 Ted Holt
When IBM adds a new feature to the RPG compiler, they do so for a reason. That’s why I try to learn new techniques. I hope they’ll improve the quality of the source code I write. One relatively new feature that I do not see widely used is the qualified file. In the following paragraphs, I’d like to tell you why I like qualified files and how to use them.
To understand the need for qualified files, it may be good to begin with a brief lesson on the history of the RPG language. When RPG was originally developed, the …
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Guru: What Do People Have Against Timestamps?
August 3, 2020 Ted Holt
In my work I often see database tables and physical files with related date and time fields (columns). By related, I mean that the two fields together indicate a certain time on a certain date for a certain event. I have found these date/time pairs to be difficult to work with at times, so much so that I have come to prefer timestamps.
I wonder why database architects (I use the term loosely) specify separate date and time fields rather than a timestamp. Having done no scientific survey, I can only guess. I suspect that many tables date back …
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Guru: Graphical Debugging Through ACS
June 8, 2020 Ted Holt
ACS (IBM i Access Client Solutions) keeps getting better and better. I can’t stay up-to-date with the latest releases of all the software I use, but I do everything I can to keep up-to-date with ACS. One of the handiest of the relatively most recent releases is the ability to access IBM i Debugger through Run SQL Scripts. If you haven’t tried IBM i Debugger, you’re missing out.
IBM i Debugger (a.k.a. System Debugger) is part of the IBM Toolkit for Java. It’s graphical, and it makes the green-screen debugger (STRDBG) look like something built by cavemen. To show you …
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Guru: A Simple, Effective Way To Compare Data Using SQL
April 20, 2020 Ted Holt
One thing I have learned over the years is that no matter how much technology changes, people always ask the same questions like: “Why does the computer say we have 50 widgets when we only have 45?” and “Can you tell me who changed the due date of order number 12345?” and “How do sales of widgets this year compare to the same time last year?” It is the last of these that I wish to address today.
Comparing data is a very common activity. Everybody compares data: sales people, production people, purchasing people, and of course management people. This …
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Guru: SQL Checks For Control Breaks
April 6, 2020 Ted Holt
A control break occurs when the combined value of one or more fields changes from one row (record) to the next when reading a data set sequentially. I used to write RPG programs with control breaks often. Now that reports are less common, I write them less often, but that’s not to say I never write a program with control breaks.
When I first learned to handle control breaks in RPG, I used the L1 through L9 level indicators. These worked wonderfully and fed my family for several years. When I moved from the System/36 world to the S/38 (and …
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Guru: SQL Can Generate A Series
March 16, 2020 Ted Holt
Most of my work is run-of-the-mill, same-old-same-old, more-of-the-same. I’m not complaining. Most of life is mundane and routine, and that’s as it should be. Too much icing ruins the cake. But sometimes I get a challenge, and when that happens, programming can be fun.
Today’s article comes out of such an experience. I needed a table with a week’s worth of dates in it. I could have written an RPG program, but I knew that SQL could handle the task. Today I’ll show you a couple of methods that you can use to generate a series of whole numbers and …
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Guru: In Pursuit Of Reasonable Data
March 9, 2020 Ted Holt
My awareness of the indifference of computers toward the reasonableness of data dawned when I enrolled in the university. The band director told me to sign up for band and jazz band for zero semester hours. He said the stupid computer wouldn’t know that no one takes a course for zero hours, wouldn’t flag me to obtain permission from the dean to carry an overload, yet would grant me the credit. He was right.
Love ‘em or hate ‘em, we live with them, we learn to get around them when they limit us, and we deal with them when they …
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Guru: Alternate SQL Row-Selection Criteria Revisited
February 24, 2020 Ted Holt
At the RPG & DB2 Summit last October, I chanced to overhear Rob Bestgen of IBM telling Paul Tuohy of System i Developer about a practice that he and others in IBM Lab Services had seen, a practice which they found horrifying. “Oh, no!” I thought. “I’ve written about that for itjungle.com!” Are you ready to be horrified?
Rob was telling Paul that they have seen SQL queries in which portions of the WHERE clause are enabled or disabled through the use of switches. I did not invent this technique — I realized more than a few years ago that …
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