Password hashes: Fixed-length binary fields or single string field?
There are 2 bits of information. This means 2 fields. It is that simple.

In practical terms, selecting 2 columns is zero extra complexity. Having to read a large field to parse one bit out is unnecessary complexity and performance overhead.

A couple of SO questions on storing salts with hashes


https://stackoverflow.com/q/1219899/27535
https://stackoverflow.com/q/1191112/27535