we made a software 1.0 with advanced installer,
but now we want to update it to 1.01 because of a little bug.
there is only one file changed, so can we do update with only the file?
This can be done through a patch. Note that we have a patch tutorial which explains what you need to do in order to create a MSP patch. Also, you need to make sure that the target and upgraded packages respect the patch rules.