is there a Recordcount for records modified inside transactions?

[sean smith]

I want to start a transaction and then attempt to update a record. If the id doesn't exists, it will fail, so I haven't updated any records. How can I figure out whether or not something was updated? I have heard of an inner-transactional "counter" that records how many records have been modified - called Recordcount, but it seems it only exists in other dbs.

I am trying to figure out if there is a way to achieve the "UPDATE ON DUPLICATE KEY" using:

UPDATE

IF recordcount = 0

INSERT

As well, I am curious if anyone can point me anywhere that I might be able to figure out what's happening behind the scenes when we do "UPDATE ON DUPLICATE KEY" - ie. is it a performance gain to use duplicate key if we look at what's actually going on?