Every table in a table hierarchy must be assigned to a named row type in a corresponding type hierarchy. Figure 31 shows an example of the relationships that can exist between a type hierarchy and table hierarchy.
However, you can also define a type hierarchy in which the named row types do not necessarily have a one-to-one correspondence with the tables in a table hierarchy. Figure 32 shows how you might create a type hierarchy for which only some of the named row types have been assigned to tables.
