NULL values same as that of zero or a blank spaces?

No. The NULL value is not the same as zero or a blank space. The following points explain their main differences:

A NULL value is a value, which is unavailable, unassigned, unknown or not applicable.It would be used in the absence of any value. We can perform arithmetic operations on it. On the other hand, zero is a number, and a blank space is treated as a character.

The NULL value can be treated as an unknown and missing value, but zero and blank spaces differ from the NULL value.
We can compare a blank space or a zero to another blank space or a zero. On the other hand, one NULL may not be the same as another NULL. NULL indicates that no data has been provided or that no data exists.