Oracle TopLink Developer's Guide 10g Release 3 (10.1.3) B13593-01 |
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Nested table types model an unordered set of elements. These elements may be built-in or user-defined types. You can view a nested table as a single-column table or, if the nested table is an object type, as a multicolumn table (with a column for each attribute of the object type).
TopLink maps nested tables with the NestedTableMapping
class. It represents a collection of object references in Java. Because of the object-relational support of the database, nested table mapping does not require foreign key information (as with a one-to-many mapping) or a relational table (as with a many-to-many mapping).
Typically, nested tables represent a one-to-many or many-to-many relationship of references to another independent structure. They support querying and joining better than the VARRAY
types that are in-lined to the parent table. TopLink supports mapping a nested table of REF
types only. TopLink does not support nested tables of basic or other structured data types–use array (see "Object-Relational Array Mapping") or object array (see "Object-Relational Object Array Mapping") mappings instead.
See "Configuring an Object-Relational Nested Table Mapping" for more information.