2023
https://www.baeldung.com/hibernate-inheritance
    https://github.com/eugenp/tutorials/tree/master/persistence-modules/hibernate-mapping

    @MappedSuperclass (no @Entity)
        This (base) class no longer has an @Entity annotation, as it won't be persisted in the database by itself.
        Childrens will just duplicate columns for inherited fields


    for @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
        @DiscriminatorColumn (at base class), @DiscriminatorValue
        DiscriminatorFormula

    for @Inheritance(strategy = InheritanceType.JOINED)
        The disadvantage of this inheritance mapping method is that retrieving entities requires joins between tables,

    for @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
        The resulting schema is similar to the one using @MappedSuperclass.
        But Table per Class will indeed define entities for parent classes,
        allowing associations and !!!"polymorphic"!!! queries as a result.

        This is not that different from merely mapping each entity without inheritance.

        The distinction is clear when querying the base class, which will return all the subclass records
        as well by using a UNION statement in the background.

        The use of UNION can also lead to inferior performance when choosing this strategy.
        Another issue is that we can no longer use identity key generation.