Syntax:
HEX(N_or_S)

If N_or_S is a number, returns a string representation of the
hexadecimal value of N, where N is a longlong (BIGINT) number. This is
equivalent to CONV(N,10,16).

From MySQL 4.0.1 and up, if N_or_S is a string, returns a hexadecimal
string representation of N_or_S where each character in N_or_S is
converted to two hexadecimal digits.
