171032 Script to modify MySql field

I need a little script that I will can run every now and then that will reset a field in my database to 0. They have the numeral 1 in some and the numeral 0 in others and some may be just blank. I know that this has to do with the update command and not that real complicated, but I am not just sure how to do it. The script will need to reset this field for every entry in that field in my database. If I am not explaining correctly, please feel free to ask in PMB.