Difference between NULL and Empty - response (1) by M.Saeed Khurram

hi,
You know well about the null, it is absolutely absense of a value, and if you find the meaning of empty the google defines it as "containing nothing; not filled or occupied" So you can say NULL is a relational databases term for empty. 
I dont know why are you comparing empty and null. if by empty you mean an empty string, for example a space, then empty string will obviosuly take 1 byte to store this as a character. But a null is complete absense of value.