Use the DROP TYPE command to remove a type from the database system. Only the owner of a type, or a superuser, is allowed to do this.
If you are logged in as a superuser, you
be able to drop system types. However, doing so can cause extreme instability. Be careful!
The DROP TYPE command will not automatically remove any objects that reference the data type, or types, that you are dropping. Once a data type is removed, anything that uses it will most likely stop working. Be sure to remove objects that depend on types that you drop, and be sure not to drop types used by objects you wish to keep.
The following command removes the zero data type from the booktown database:
DROP TYPE zero;