Figure 3-2 – Apple WebObjects 5 User Manual
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Mapping Your Enterprise Objects to Database Tables
Apple Computer, Inc. January 2002
C H A P T E R 3
Enterprise Objects
Figure 3-2
Mapping between an enterprise object class and a single table
In actual practice, the mapping is more flexible than this. For example:
■
You can map an entity to a single table, a subset of a table, or to more than one
table. For instance, you can map a Person entity’s
firstName
and
lastName
attributes to a
PERSON
table but its
streetAddress
,
city
,
state
and
zipCode
attributes to an
ADDRESS
table.
■
Generally, an attribute is mapped to a single column, but the
column-to-attribute correspondence is similarly flexible. You can map an
attribute to a derived column, such as
price * discount
or
salary * 12
.
■
You can map an entity to one or more tables.
In addition to mapping tables to entities and columns to attributes, WebObjects
maps primary and foreign key columns to relationships between objects.
WebObjects defines two types of relationships—to-ones and to-manys—which are
both illustrated in
. The relationship a MovieRole has to its Movie is a
to-one relationship, while the relationship a Movie has to its MovieRoles is a
to-many.
1132
Feldman
Corey
1028
Farina
Dennis
TALENT_ID
LAST_NAME
FIRST_NA
ME
TALENT
Talent
lastName "Farina"
firstName "Dennis"