What is the difference between NULL and NULL in MySQL?

What is the difference between NULL and NULL in MySQL?
1: When count () is used to count the number of records in a column, if the NULL value is used, the system will not automatically ignore it, but the NULL value will be counted. 2: null is null or is not null. The ifnull () function can be used in SQL statement functions for processing, use = ''or <>'' to process null characters. 3. Special Considerations for MySQL and timestamp data types, if you insert a NULL value to the column inserted for this data type, the displayed value is the current system time. When a null value is inserted, '2014-00-00 00:00:00 '4 is displayed: whether the null value is determined by is null or = ''depends on the actual service. 5: NULL value ('') does not occupy space. 6: NULL in MySQL actually occupies space.