Comments - Does MariaDB support User Defined Types (UDTs)
Content reproduced on this site is the property of its respective owners,
and this content is not reviewed in advance by MariaDB. The views, information and opinions
expressed by this content do not necessarily represent those of MariaDB or any other party.
No, user defined types are not supported in MariaDB. There is a request to support it, MDEV-10143, but no timeline yet.
Content from the SQL-99 book clearly says that it's about the standard, not necessarily supported in MariaDB. It's listed on the KB as the book contents have been made available and may be of interest to people.