>> So in the UPDATE statement, I only provided a value for last_user. But the
>> first test of the trigger function tests for a NULL value of
>> NEW.empname. Since
>> I did not provide one, I was expecting it to be NULL and an exception to
>> be thrown. Am I just misunderstanding how things work? Is there any way to
>> test to see if the UPDATE statement contained a reference to empname? If the
>> answer is no, I can certainly work with that, but before I go on I wanted
>> to make sure I wasn't missing anything.
>
>
> An UPDATE in Postgres is really a DELETE/INSERT where the OLD row is deleted and the NEW one inserted with the OLD values unless they where explicitly changed. So
Shoot, I went totally brain-dead on that one. I forgot that I'm actually doing
a DELETE/INSERT, and the behaviour makes perfect sense in that light. It's
called MVCC. Thanks for setting me straight!
> in your test NEW.empname is still 'John Doe' and therefore NOT NULL. That test would only work if someone explicitly set empname = NULL in the update. If you want to check whether the value has not been changed then:
>
> IF NEW.empname = OLD.empname THEN
That's exactly the solution I hit on. Back to work, and thanks again.>> first test of the trigger function tests for a NULL value of
>> NEW.empname. Since
>> I did not provide one, I was expecting it to be NULL and an exception to
>> be thrown. Am I just misunderstanding how things work? Is there any way to
>> test to see if the UPDATE statement contained a reference to empname? If the
>> answer is no, I can certainly work with that, but before I go on I wanted
>> to make sure I wasn't missing anything.
>
>
> An UPDATE in Postgres is really a DELETE/INSERT where the OLD row is deleted and the NEW one inserted with the OLD values unless they where explicitly changed. So
Shoot, I went totally brain-dead on that one. I forgot that I'm actually doing
a DELETE/INSERT, and the behaviour makes perfect sense in that light. It's
called MVCC. Thanks for setting me straight!
> in your test NEW.empname is still 'John Doe' and therefore NOT NULL. That test would only work if someone explicitly set empname = NULL in the update. If you want to check whether the value has not been changed then:
>
> IF NEW.empname = OLD.empname THEN
