Well, it depends. Some RDBMS's don't store the string's length with each value for fixed-width character fields. So a fixed-length field may still be preferabl

Well, it depends. Some RDBMS's don't store the string's length with each value for fixed-width character fields. So a fixed-length field may still be preferable if the space lost to padding amounts to less than the space lost to overhead. That distinction doesn't apply to PostgreSQL, because it stores a length along with the value even for fixed-with columns.