Wednesday, June 29, 2022

Change to Create Table statement to stop accidental deletion of the Table

stop table delete with restrict on drop

It is always a danger that someone will accidentally drop (delete) the wrong file, not maliciously just accidentally.

02    (COLUMN1 CHAR(1)) ;


Statement ran successfully

Within the new release of IBM i 7.5 is an addition to the Create Table statement that can prevent this. This does appear to be only in 7.5, I cannot find a mention of this in the documentation for IBM i 7.4 TR6.

This addition to the Create Table statement is: WITH RESTRICT ON DROP

Tuesday, June 28, 2022

Moving content of data structure into an array

data strucutre subfields in array

I have been asked this same question a few times during the last couple of weeks: What is easiest way to move data from a data structure's subfields into an array?

Asking some other people I know how they would do it, several of them did not know of this simple way.

Here is the start of my code:

Wednesday, June 22, 2022

Removing duplicate characters from a string

rpg scan replace %scanrpl

I was asked how I would remove duplicate characters from a string just using RPG. I has been some time since I came up with an all RPG solution, so I accepted the challenge.

The string of data is in a file, TESTFILE, in the field F1. The sample string I used in F1 was:



I have more than one of these characters in the string: a, b, c, and d. And only one of these: f, g, h, i, j, k, and l. My goal is for a single character of all of these.

Tuesday, June 21, 2022

Extra parameters added to Call command to prevent decimal data error

new parameters added to call command

Anyone who has programmed on IBM i has experienced this frustration. I want to call a CL program from a command line. I type:

CALL CL_PGM ('A' 12)

And I am presented with the following error:

MCH1202 received by procedure CL_PGM. (C D I R)

For the beginner this is cryptic. When I drill down into the job log I can see what really happened:

Friday, June 17, 2022

More fun with the Boolean data type

using unknown instead of null in sql

IBM i 7.5 introduces a synonym for NULL, UNKNOWN. Having performed a few tests, I can confirm I can use it just as I would NULL.

For example I can use it when inserting data into a SQL Table. The first column in this Table is a Boolean data type, the second is character.


I have used a multiple rows insert to insert six rows with one Insert statement. Notice how I have used UNKNOWN in the data for the last row to be inserted.

I check the contents of this file with the following SQL statement:

Wednesday, June 15, 2022

New data type for SQL - Boolean

sql boolean data type

A new data type has been added to Db2 for i's Data Definition Language, DDL, as part of IBM i 7.5, but was not added to IBM i 7.4 TR6. A Boolean data type.

Being Boolean it should only contain two values, but this can contain three possible values:

  1. True
  2. False
  3. Null – when this contains no data

I love this. For many, many years I have been creating "Boolean" like columns or fields to contain a sorta kinda true/false logic. But as the columns/fields were either character or numeric they could contain any valid value of that data type. Now I can have a column to denote things like:

  • Item is in-stock
  • Item is in a backlog status
  • Certain information has been provided or accompanies whatever

You get the idea.

A Boolean column can be defined in a SQL table as simply as:

Friday, June 10, 2022

9 years and counting!

Wow! It was nine years ago I wrote the first post of this blog. Here I am almost 800 posts later and I am still writing. Fortunately, IBM has "cooperated" and has released a lot of really interesting and exciting things in this time, giving me lots of material to write about.

This where I pick my favorite five posts of the past 12 months, which is always a struggle as there is always so many things to consider:

Wednesday, June 8, 2022

New RPG op-code to send messages to job log

rpg snd-msg %msg %target

Another addition to the RPG programming language with IBM i 7.5 and 7.4 TR6 is an operation code that allows me to write to the current job's job log.

I have been using the SQL procedure LPRINTF to write to the job log since 2019. Now I have the ability to do so with native RPG.

The new operation code is called Send Message, SND-MSG, and is accompanied by two new optional Built in Functions, BiF: %MSG and %TARGET.

Just how simple it is to write to job log I will demonstrate below. Let me start with my first example program's source code:

01  **free
02  dcl-s Text varchar(50) inz('Second message') ;

03  snd-msg 'First message' ;

04  snd-msg Text ;

05  snd-msg *INFO 'Third message' ;

Wednesday, June 1, 2022

New SQL built in function allows for validating data types

sql try_cast cast

I am sure many of us have found that when we try and cast, in SQL, from one data type to another the “casting" will fail. This is especially true when moving character representations of numbers or dates to a decimal or date type. With the new release IBM i 7.5 and 7.4 TR6 there is a new SQL built in function that allows for the testing of a cast before it is performed.

Before I start explaining this new built in function let me define the table I will be using, TESTTABLE:

 COLUMN2 CHAR(10)) ;

It has two columns I will be using in this post. For now, I am only interested in the contents of the column COLUMN1, which I can see using the following SQL statement: