what is difference between NULL and Empty in mysql

Question

What is difference between NULL and Empty String in Mysql ?

How much storage space it will take ?

For Example .

In the user table

name : NULL - How much space its take

phone : -How much space its take

Answer 1

The best way to think about NULL is that it is poisonous.

Any operation done with NULL will produce NULL.

NULL + any number type is null. NULL concat any string is null.

An empty string is a string with length of 0.

Example:

mysql> select concat('hello world', null);
+-----------------------------+
| concat('hello world', null) |
+-----------------------------+
| NULL                        |
+-----------------------------+

mysql> select concat('hello world', '');
+---------------------------+
| concat('hello world', '') |
+---------------------------+
| hello world               |
+---------------------------+

As for space saving it depends on the datatype the column is defined.