A common occurrence I have noticed in MySQL apps is that MD5 values are stored as 32 byte values rather than 16. Just to ‘rehash’, an MD5 value is a 16 byte hexadecimal value, typically used as a unique fixed-length signature of a string, useful for identifying unique strings or one-way encryption of passwords. The binary representation takes 16 bytes (e.g.
BINARY(16)), though a human readable hexadecimal version takes twice as many (e.g.CHAR(32)).
Same goes for IPv4 address, which can be stored as UNSIGNED INT (4 bytes) instead of VARCHAR(16) (16 bytes)