Oracle’s Deviations From the RulesThe most famous offering from Oracle is its relational database, which also brings Oracle the most profits. As the second-largest software giant (after Microsoft), Oracle has some of its own conventions which may or may not be consistent with other generally accepted conventions. Maybe that’s the reason why so many don’t understand Oracle.First of all, Oracle doesn’t follow the SQL standard. In many computer science courses, students practice and learn the fundamentals of databases using an Oracle database. It just so happens that even I myself have seen a lecturer shrugging his shoulders when speaking about Oracle odd behaviours.
I like Oracle database. It is efficient, easy to use for beginners and professionals – its tools for query analysis and optimization are masterpieces. But it has a very annoying “feature” – empty text (containing 0 characters) is stored in the database as null.Where did such a feature come from?Probably from the ancient ages, just after the dawn of time, i.e., the late 70’s  . In that age, memory (RAM and disks) was very limited and system designers did their best to use as little memory as possible. In old versions of Oracle DB,
Recently a fellow database architect claimed that in Oracle the typeVARCHAR2(255)means a string of 255bytes, not characters. There is not much difference between the two in the English-speaking world. It matters though if you want to handle people with names like Kołłątaj . (Not that Hugo Kołłątaj – a famous Polish 18th century politician – would ever use any of our systems, but he became our byword for all non-pure-ASCII names). I was very surprised by what the architect said and I decided to further investigate the matter.