EER> For instance, in the following update statement:

EER> update table set a = 'x' where id = 123;

EER> if no rows were modified one doesn't know if that was because EER> there already is a row with id = 123 and a = 'x', or if the

Hmmm... If you do such a query on the mysql command line, it does tell you how many matched and how many were modified. This implies that the API provides some method to do this, as the mysql client is just that -- a client written using the API.

So, at worst, you would read the sources to the mysql program to see how it accomplishes this task. I'm sure the manual also has info on it.