Ted Holt
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Guru: Where’s The Table?
September 14, 2026 Ted Holt
It began with an irritation. I considered it a simple request. “Which file did my SQL query read?” I was using the Run SQL Scripts tool to modify an SQL query with unqualified table names. And yet I knew of no ready way to determine the schema (library) name of any of the files. How was I to know which tables I had just queried?
Let me back up a bit. My SQL client of choice is the Run SQL Scripts tool, which is part of IBM’s Access Client Solutions (ACS). It is not unusual for me to copy and …
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Guru: Claude’s SQL Tip
August 10, 2026 Ted Holt
Today’s tip comes to us from Claude, as in the AI chatbot created by Anthropic. I don’t need to introduce him. Many readers of this august publication are far better acquainted with him than I am. I have heard reports of IBM i programmers who have quit writing source code, telling Claude to write it for them. Some folks seem to be right proud of that fact. Furthermore, I’m told that some places no longer allow humans to write source code.
I had a few ideas in mind for this article and was weighing the merits of each one when …
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Guru: Where’s The Table?
June 8, 2026 Ted Holt
It began with an irritation. I considered it a simple request. “Which file did my SQL query read?” I was using the Run SQL Scripts tool to modify an SQL query with unqualified table names. And yet I knew of no ready way to determine the schema (library) name of any of the files. How was I to know which tables I had just queried?
Let me back up a bit. My SQL client of choice is the Run SQL Scripts tool, which is part of IBM’s Access Client Solutions (ACS). It is not unusual for me to copy and …
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Guru: DateTime Rules Of Thumb
May 18, 2026 Ted Holt
I am not a great programmer. I am a decent programmer who has found ways to stay out of trouble. I use many little rules of thumb to keep me and the people I serve from being unpleasantly surprised at inopportune moments. Today I share rules of thumb regarding datetime data that have served me in my work.
The first date field I used in an RPG program was a six-digit zoned-decimal value in MMDDYY format. This was part of a programming assignment for a class I was taking at the local vocational-technical center in days of yore. In my …
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Guru: Load A Varying-Dimension Array With One SQL Fetch
May 11, 2026 Ted Holt
One thing I really like about working in different shops is the vast amount of source code I’m exposed to. But that’s not the best thing. The best thing is the people I meet and get to know. The more clients, the more teachers. Combine source code and people, and my life, personally and professionally, is enriched.
Today I’m pleased to pass along an SQL technique I picked up from the IT shop of a manufacturer. The programmers use this technique to load subfiles from SQL cursors in RPG programs. It works in client-server applications as well. It combines a …
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Guru: Assertions, Take 2
February 12, 2024 Ted Holt
It’s been almost 20 years since Cletus the Codeslinger introduced assertions to the IBM midrange world, and in that time, I have included many assertions in my RPG programs. During that 20 years, RPG has changed a bit and Cletus has quit writing articles (but not source code), so I’ve taken it upon myself to update the code he gave us.
First, however, it might be a good idea to briefly review the topic of assertions for readers who don’t know what they are. An assertion is a program statement or command that cancels a program if a fatal condition …
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Guru: Using Mixed Lists To Add “Data Structures” To CL Commands
January 15, 2024 Ted Holt
I can’t remember the last time I worked on an RPG program that had no data structures, but it was probably on a System/34. Everybody uses data structures, and with good reason – they are as handy as a pocket. When writing CL commands, it is possible to include parameters that are formatted as data structures. IBM calls them mixed lists. In the following paragraphs, I show how this is accomplished.
You may not realize it, but you have used IBM-supplied commands that have mixed-list parameters. For example, the Copy File (CPYF) command has several such parameters: FROMKEY, TOKEY, INCCHAR, …
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Guru: TryIT – You’ll Like It
October 2, 2023 Ted Holt
I have watched children play Whac-a-mole, but I’ve never played it myself, perhaps because the game unpleasantly reminds me of programs that I have had to work on. I fix one bug, only to see another bug rear its ugly little head. Life’s too short to endure such nonsense. Besides, it is embarrassing for someone to tell me that the program I supposedly just fixed is still broken.
Suppose you’re working on a 4,000-line RPG program and you comment out lines 650-660. What you don’t realize at the time is that a variable used in line 2755 has to …
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Guru: Aliases — Underused and Unappreciated
October 3, 2022 Ted Holt
One of the first things I learned about programming in the RPG II language was that field and variable names had to be six characters or less and they did not have to be pronounceable. I accepted this without question, as I was new to computers and figured that everything that had to do with computers was arcane and other-worldly. It wasn’t until I began work toward my computer science degree and was privileged to learn Pascal that I came to appreciate the value of longer identifier names, and of clarity of source code in general.
You don’t have to …
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Guru: Beware of SQL Precompiler Variables
September 26, 2022 Ted Holt
In a famous Henny Youngman joke, a patient says, “Doctor, it hurts when I do this,” to which the doctor replies, “Then don’t do that.” Corny jokes aside, I have spent decades trying to identify programming practices that hurt when I do them, and having identified them, cease to do them. A case in point is the misuse of the variables that the SQL precompiler defines in my RPG programs, variables such as SQLCODE, SQLSTATE, and SQLER3.
“So what,” I hear you ask, “is the problem with these variables? ” Well, they’re global, and global variables are evil. Global …
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