It may be wrongly named (to our eyes), but that's what Hibernate was
calling it. (Some of these may have also come from Toplink as well).
If it makes you feel better call it "Hibernate table-per-subclass" and so on.
On 5/31/07, Lachlan Deck <lachlan.dec..mail.com> wrote:
> On 01/06/2007, at 9:37 AM, Aristedes Maniatis wrote:
> > Is that terminology right? That page says:
> > * single-table == flat == table-per-class-hierarchy
> Easily true.
> > * Vertical == table-per-subclass
> That is wrongly named. That is horizontal inheritance where the
> parent doesn't map to a table. Vertical involves parent and kids each
> having their own table. (See http://developer.apple.com/documentation/
> WebObjects/UsingEOModeler/index.html as an example)
> > * Horizontal == table-per-concrete-class
> Correct, though hazy terminology for mine seeing as vertical also has
> a table for the parent.
> The JPA for better or worse has:
> - Inheritance.SINGLE_TABLE. That's the easy one.
> - Inheritance.JOINED. Most definitely == vertical.
> - Inheritance.TABLE_PER_CLASS. This is (for mine anyway) an unclear
> name given that JOINED is also a table per class. It would have been
> clearer if they'd chosen TABLE_PER_SUBCLASS.
> > My page says:
> > * single-table
> > * horizontal == table-per-class
> > * vertical == joined
> That is correct.
> From the JPA:
> Joined: A strategy in which fields that are specific to a subclass
> are mapped to a separate table than the fields that are common to the
> parent class, and a join is performed to instantiate the subclass.
> Table-per-class: A table per concrete entity class.
> As additional support for this... see also description here (http://
> java.sys-con.com/read/286901.htm) which documents them a little more
> verbosely as:
> SINGLE_TABLE: Single-table-per-class inheritance hierarchy. This is
> the default strategy. The entity hierarchy is essentially flattened
> into the sum of its fields, and these fields are mapped down to a
> single table.
> JOINED: Common base table, with joined subclass tables. In this
> approach, each entity in the hierarchy maps to its own dedicated
> table that maps only the fields declared on that entity. The root
> entity in the hierarchy is known as the base table, and the tables
> for all other entities in the hierarchy join with the base table.
> TABLE_PER_CLASS: Single-table-per-outermost concrete entity class.
> This strategy maps each leaf (i.e., outermost, concrete) entity to
> its own dedicated table. Each such leaf entity branch is flattened,
> combining its declared fields with the declared fields on all of its
> super-entities, and the sum of these fields is mapped onto its table.
> with regards,
> Lachlan Deck
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