Andreas Terrius <gotenwinz99@gmail.com> writes:
> Is there any way to check whether the row already exists before checking
> constraints ? I still want it to fail if it turns out to be a new row
> (which would violate the not null constraint), but updates the row if it
> already exists.
I'm not really sure why you expect this to be able to work. The data
you are supplying is insufficient to satisfy the INSERT case, so why do
you think that an insert-or-update should be possible?
ISTM that you could try the UPDATE first and notice whether it updates
any rows or not. I'm not sure what you're going to do if it doesn't,
though, since you still haven't got enough data to do an INSERT.
regards, tom lane