NULL in MySQL (Performance & Storage)

Question

What exactly does null do performance and storage (space) wise in MySQL?

For example:

TINYINT: 1 Byte TINYINT w/NULL 1 byte + somehow stores NULL?

Answer 1

dev.mysql.com/doc/refman/5.0/en/is-null-optimization.html

MySQL can perform the same optimization on col_name IS NULL that it can use for col_name = constant_value. For example, MySQL can use indexes and ranges to search for NULL with IS NULL