what is differenct between null and space in sql table?

Answer 1

when you set a cell value to null that mean this cell is has no value
but when I put space or empty string that means that this cell has a value which is space or an empty string

for example if I have a field called Company Name
if I set null value on this field that means the name of this Company is unknown or missing
but if i set its name to space or empty string that means this Company's name is known and not missing and this name is "space"

Answer 2

NULL is a condition where the value of a field is missing. Therefore you can't do a calculation on a field that's set to null because you have no value.

Whereas a space is a character.

I'm linking a short article that explains the reason for null.

Answer 3

I don't know about SQL for sure, but in most programming senses, NULL means that there is literally nothing there at all (or zero if shown as a number), and a space means a single character: " " a space - different from null.

Answer 4

Yea, NULL is nothing, space is a space. When printed you may not be able to tell the difference, but they are different. NULL is 0 is ASCII which means nothing is there at all, and a space is actually 32 for ASCII, so for a space there is actually something there.