Wednesday, September 25, 2019

Creating many different dates, days, months, and years in just one SQL statement

calculating different dates using sql

The germ for this post came from a program I found that was used in a job I was making changes to. The program made a data structure of information about various dates, you'll see exactly what below, that was passed to various programs. The program was several thousand lines of unnecessarily complicated RPG code. Looking at the results it was passing back to the calling program I knew it could be done a lot simpler using SQL, rather than the complex calculations this program contained.

Never one to turn down a challenge over the weekend I wrote a SQL RPG program that generates the same information in the data structure just using one SQL Select statement. I thought this would be an interesting thing to share due to some of the SQL functions I used, some I have written before others I have not, and you might find useful if you have to do something similar.

When called this program returned a data structure that contained the following:

Wednesday, September 18, 2019

Using SQL to rank results

ranking results using sql rank()

When I wrote about using a SQL Sequence to place sequential values in a column I used the example of ranking students based upon on their test results. Looking back this may not have been the best example, as if two students had the same score they would have been given a different sequence number.

Fortunately SQL does have a function I can use to properly rank these students, based on their test scores.

Let me start with the students and their test scores:

---------  ----------  -----------  -----
FUESTER    MAX                      25.69
ECKERT     TRISTAN          M       49.86
APUZZO     CAROL            C       14.89
TORRES     JOSE                     94.96
PENA       JUANITA          M       74.09
HONG       XIA                      18.54
REED       STEVE            J       65.83
OKEEFE     VINCENT                   6.02
KING       CATHERINA        K       18.76
WILEY      CHRISTIAN        J       60.77
MORALES    MARIA            A       65.83

Steve Reed and Maria Morales have the same test score, therefore, they need to have the same ranking. Let me show the SQL statement I would use to rank these eleven students by their score.

Thursday, September 12, 2019

End of support for IBM i 7.2 is announced

end of life for ibmi release 7.2 in 2021

On September 10 IBM announced the end of marketing of IBM i 7.2 on April 30, 2020, and the end of support for this release effective April 30, 2021.

IBM i 7.2 was released in May 2014, and by 2021 it will have had a life of 7 years.

If you have partitions running IBM i 7.2 it is time to determine if your Power server can support the newer releases 7.3 and 7.4, and if it does to start making plans upgrade to one of those newer releases.

You can read the announcement document from IBM here.

Wednesday, September 11, 2019

Using SQL to determine which subsystems are active or not

list all subsystems and whether they are active

When I wrote about how it is possible to check if a subsystem is active or not someone asked me if there is a way to list all the subsystems and whether they are active or not.

Having had some time to "play" I have developed a way of doing this by combining data from the following two SQL table functions:

I can get a list of all subsystem description objects by using the OBJECT_STATISTICS table function:

Wednesday, September 4, 2019

Variable length arrays in RPG

arrays with varying number of elements

One of the new additions to RPG in IBM i 7.4, and not to the equivalent TR of 7.3, was the ability to have variable length arrays.

Having read the documentation, and having had a chance to "play", my findings mean I can divide this post three sections:

  1. Setting the number of elements in the array
  2. Expanding number of elements
  3. Compile time array

Before I get started I want to show what the maximum size of an array, this number has not changed since at least IBM I 7.2 . It is not the number of elements in the array that is the limit, it is the total size of the array. The array must not exceed 16,773,104 bytes. For example, this is valid as an array of 16,773,104 elements of one character is valid.