Tom Lane wrote:
>> I don't have handy a spec guide. Does this mean that MySQL
>> is indeed showing incorrect behavior?
>
> I think this is really outside the spec.
[...]
> There is not anything I can see addressing whether an
> "update" should or should not be considered to occur if a
> target column happens to not change as a result of a
> commanded update.
Moreover, I can think of one argument why an UPDATE that
does not change the value of the row should still occur:
There may be an ON UPDATE trigger on the table that you
expect to fire whether or not the UPDATE was "optimized
away".
Yours,
Laurenz Albe