Wednesday, May 23, 2018

How to SQL table's long names in RPG program

using long column names from sql table

The seed for this post came from a conversation I had with one of my work colleagues. He complained that even though he could give the columns (fields) in a DDL (SQL) tables names longer than ten characters he found that it was hard to use these names in programs, especially those using printer or display files.

He is not the first person who had made this observation to me. Over the time I have written this web site others have made the same observation.

Let me show what I shared with him so that he could easily overcome this perceived shortcoming.

Monday, May 21, 2018

New Technical Refreshes coming in September?

While poking around in IBM's developerWorks wiki I noticed that pages for the next Technical Refreshes for IBM i 7.3 and 7.2 have already been added.

Wednesday, May 16, 2018

Deleting the current row when using cursor

delete current sql cursor row

In a previous post I wrote about how to perform an update of the current row/record when using a SQL cursor in a RPG program. I have been asked what could be considered the obvious follow on question: How I delete the current row/record when using a SQL cursor?

Fortunately it is as simple as the Update process. All I need to do is...

  • Define the cursor
  • Open the cursor
  • Fetch from the cursor
  • Delete
  • Close the cursor

In its simplest form a program could just be like this:

Wednesday, May 9, 2018

Creating a XML file

create xml file using sql and rpg

In an earlier post I described how to retrieve information from a XML file. This left me thinking how do I create a XML file just using native IBM i functionality?

I wanted to keep my program simple, K.I.S.S. After a good deal of research I have an example program of 28 lines, which takes data from a DDS file or DDL table, converts the data to XML, and outputs the data to a file in the IFS. I need acknowledge Birgitta Hauser here. She is someone whose work I study, and articles I always read. Some of the code in this example is based upon a series of example procedures and programs she posted on Github. I will post a link to her Github at the bottom of this post along with the other reference links.

Before I continue I want to describe the parts of a XML document so you understand when I call an element something what it is. Below is an example of a XML document:

Wednesday, May 2, 2018

Update the current row when using cursor

updating current SQL cursor

I was asked how to update the current row if I am "reading" a file/table using a SQL cursor. At first this question took me aback, it was not that I did not know how to do it, but more a question of why?

What I consider to be one of the biggest benefits of using SQL to process (fetch, delete, and update) data from your database in sets, "chunks" of data. If I need to process a hundred rows/records of data why get each one individually? as that would be a hundred I/O operations. I can get all hundred rows in one I/O operation, thereby, reducing the amount of time and system resources needed to get the data.

I spent some time thinking of a scenario where I might want to fetch rows/records one at a time. I came up with the scenario of an interface. One program would add data to a file, and another would retrieve the data from the file and process the transaction. My example will be that second program.

Wednesday, April 25, 2018

Easy to create shortcut commands

creating your own shortcut commands

After my post about how to create your own commands I received messages from readers giving me examples of how they have created their own shortcut commands, to do the same as the standard IBM i command but shorter. In one example the command SP did the same as WRKSPLF.

I don't think many people know of proxy commands. These allow me to create shortcut commands of the regular IBM i commands without any programming. You can even make proxies of proxy commands, although I cannot think of a reason why I would ever think to do so.

In this example I am going to create a proxy command, SP, for the Work with Spooled Files command, WRKSPLF.

Wednesday, April 18, 2018

Sending your own program created messages to the error subfile

filling the error subfile, errsfl, with program generated message

I have previously written about using the error subfile to display error messages, rather than the message subfile. Personally I like using the error subfile as it is another case of allowing the operating system to do the work for me.

Since publishing that article I have received messages asking how can people create their own error message text, in the RPG program, that is displayed in the error subfile.

Fortunately there is a simple way to do this that will work in either RPG in CL.

No matter which language I use the display file can be the same. Here is the display file I will be using in this example.

Wednesday, April 11, 2018

Built in function to return name of procedure

%proc built in function to return procedure name

Until the last round of Technical Refreshes, IBM i 7.2 TR7 and 7.3 TR3, I could not find a way to retrieve the name of the procedure that I was in. The program data structure enticed me with the *PROC keyword. This was not the procedure's name, but rather either the program's or module's name.

01  DPgmDs           SDS                  qualified
02  D ProcName          *PROC

01  dcl-ds PgmDs psds qualified ;
02    ProcName *proc ;
03  end-ds ;

Fortunately these two Technical Refreshes introduced a new built in function, BiF, to returns the name of the current procedure: %PROC

This example is of what I call a closed subprocedure and how this new BiF works.

Wednesday, April 4, 2018

Handling nulls in CL

in a cl program how to handle a null value from a file

I have written previously about how to handle nulls values in RPG and in SQL, but until this week I had never had a problem with null in a CL program.

The CL program was "reading" a SQL table, where some columns/fields were null.

01 PO18087       P            145.67
02 PO18556       C             15.36
03 PO18223       -                  -
04 PO18777       D                  -

The CL program is simple.

Happy patron saint's day!

Today is the saint's day of Saint Isidore of Seville.

In 1997 Pope John Paul II, of the Catholic Church, decided that computers and the internet needed a patron saint. His choice was St Isidore of Seville, "the last of the great scholars of the ancient world".

I hope you all have a good St Isidore Seville day. But if you need divine intervention for your computer problem this is the day could be the right day to ask for divine inspiration.

To learn more about St Isidore of Seville see here.

I need to say "St Isidore of Seville" rather than just "St Isidore" as there is another saint of the same name, "St Isidore the farmer", who is the patron saint of farm workers and the communities they live in.