如何将未选中的值定义为复选框？

I'm trying to set a default value for 'unchecked', but is not working. I wanted it. If checked stores = 'Yes', if unchecked stores = 'No'. I do not know why not be working. The inputs in database are inserted always with value 'Yes'. Even though they checked or unchecked.I'm trying to set a default value for 'unchecke