Adding variables to ad-hoc SQL queries with REXX

It’s incredible how easily I can be distracted. All I needed was a quick and dirty way of capturing the input into an interface and now I’m writing a blog post.

Everything starts with an issue and, in this case, the issue is with an interface not behaving as expected in production even though everything works as expected in the test environment. My suspicion is that the incoming data is not correctly formatted, causing transactions to not meet the selection criteria. But to confirm this, I need to see exactly what is waiting to be processed when the interface runs.

Since this interface runs after the end of business I want to be able to submit an SQL query to capture the input data into a separate table so that I can see what was processed when I come in tomorrow morning. And, because much of this data is not destined to pass through the interface in question (this is why we have selection criteria) I want to be able to select today’s transactions for whatever the current value of today happens to be.

In a sane world, this would be a simple case of using the current date but in the real world there are still people using eight digit numbers to represent the date. This leads to some unwieldy date calculations in SQL which led me to wondering whether I could capture this in a variable to make things a bit more readable. It turns out I can, but not on the version of the IBM i operating system that I am currently using.

What really caught my eye at the above link however, was this:

but if “ad hoc sql + variables” is the thing you need, you should really try Rexx.

And I thought: “Rexx. That’s something I haven’t used since last century.”

Any excuse to download a couple of manuals is reasonable as far as I’m concerned, so off I went.

And here’s the script (library and table names have been changed):

datenow = DATE('S')
statement = 'insert into MYLIB/INPUTDATA' ,
            'select * from PRODLIB/INPUTDATA where dhdate =' datenow
address 'EXECSQL'
EXECSQL 'SET OPTION COMMIT = *NONE, NAMING = *SYS'
EXECSQL 'delete from MYLIB/INPUTDATA'
EXECSQL statement

The DATE function returns the current date and the 'S' option handily reformats it into an eight digit number (yyyymmdd). The address 'EXECSQL' statement handily points the subsequent commands to the SQL command environment and then it’s just a case of executing the statements I need to execute.

It all works very nicely indeed.