Actually, MySQL evaluates an empty hexadecimal value to a zero-length binary string. It can be demonstrated as follows −
mysql> Select CHARSET(X''); +--------------+ | CHARSET(X'') | +--------------+ | binary | +--------------+ 1 row in set (0.00 sec)
The above result set shows that the empty hexadecimal value is a binary string. And the result set below shows that it is of length 0.
mysql> Select LENGTH(X''); +-------------+ | LENGTH(X'') | +-------------+ | 0 | +-------------+ 1 row in set (0.00 sec)