>> 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. > >> >> Thanks! > > > > -- > Adrian Klaver > adrian.kla...@aklaver.com
