Why historically do people use 255 not 256 for database field magnitudes?

Why historically do people use 255 not 256 for database field magnitudes?

sql rdbms-agnostic

sql

What are views good for?

sql view rdbms-agnostic

sql

What is the problem with foreign key cascade multiple paths and cycles?

sql foreign-keys cascade rdbms-agnostic

sql

Do you use the OUTER keyword when writing left/right JOINs in SQL?

sql syntax rdbms-agnostic

sql

SQL portability gotchas

sql database orm portability rdbms-agnostic

sql