SQL Update a Multi-Table View using INSTEAD OF Triggers

Yesterday I added another SQL trick to my bag ‘o tricks. I am currently working on fixing EDI invoicing process and I needed a way to delete records from four files based on the same key. I could have wrote RPGLE Free Embedded SQL that would have been about 60 lines of code but wheres the fun in that.

I popped open the Google window and searched on “iseries sql delete from multiple tables”. the second hit directed me to IBM and the fourth to Preform the Impossible: Update a Multi-table View using INSTEAD OF Triggers. What did we did before Google, oh yeah, read a manual!

Impossible, that’s for me. It took me a few minutes to understand and a peek at IBM documentation I had to create a view and then the trigger. Once created any time I delete from the view all associated records in the four files are deleted. Very cool.

After view and trigger created I can run this SQL interactive or embedded.

delete from yourlib.ediinvw
where ihedoc = 0000046475

My new view is EDIINVW and I am deleting by EDI document control number.

To accomplish this I created the view with the below code using SQL Explorer.

create view yourlib.ediinvw as
select ih.ihedoc, id.idedoc, ss.iaedoc, si.isedoc
from yourlib.vedinih ih
join yourlib.vedinid id on id.idedoc = ih.ihedoc
join yourlib.vediniss ss on ss.iaedoc = ih.ihedoc
join yourlib.vedinis si on si.isedoc = ih.ihedoc

The four fields in the Select statement is the key field for each of the four files.

I then attempted to create the delete Trigger. SQL Explorer did not like the syntax so I copied and pasted into the green screen iSeries SQL interactive command line. My guess is that SQL Explorer has an issue with INSTEAD OF DELETE ON.

create trigger yourlib.ediinvdel
Instead of delete on yourlib.ediinvw
referencing old as EdiInvwOld
for each row mode DB2SQL
begin atomic
delete from yourlib.vedinih
where ihedoc = EdiInvwOld.ihedoc;
delete from yourlib.vedinid
where idedoc = EdiInvwOld.idedoc;
delete from yourlib.vedinid
where iaedoc = EdiInvwOld.iaedoc;
delete from yourlib.vedinid
where isedoc = EdiInvwOld.isedoc;
end;

I learned another very cool SQL trick, Thanks IT JUNGLE and Four Hundred Guru. This will come in handy over the next few weeks as I fix the EDI processes.

Have your best day!

~Richard

In programming, as in everything else, to be in error is to be reborn.  ~Alan J. Perlis