37 Configuring a Relational One-to-One Mapping

This chapter describes the various components that you must configure in order to use a relational one-to-one mapping.

For more information, see the following:

Table 37-1 lists the configurable options for a relational one-to-one mapping.

Relational One-to-One Mapping Configuration Overview

Table 37-1 lists the configurable options for a relational one-to-one mapping.

Table 37-1 Configurable Options for Relational One-to-One Mapping

Option	Type	TopLink Workbench	Java
"Configuring Reference Descriptor"	Basic
"Configuring Method Accessing"	Advanced
"Configuring Read-Only Mappings"	Advanced
"Configuring Private or Independent Relationships"	Advanced
"Configuring Batch Reading"	Advanced
"Configuring Joining at the Mapping Level"	Advanced
"Configuring Indirection"	Advanced
"Configuring Bidirectional Relationship"	Advanced
"Configuring Mapping Comments"	Advanced
"Configuring Table and Field References (Foreign and Target Foreign Keys)"	Basic

Configuring Joining at the Mapping Level

TopLink supports configuring an inner join at the mapping level for one-to-one mappings only. When a class that owns the mapping is read, the TopLink runtime will always get the class and the target of the one-to-one mapping with one database hit.

Use this feature only if the target object is always required with the source object, or when indirection is not used.

You can also configure join reading (see "Join Reading and Object-Level Read Queries") at the query level.

For more information about joins, see "Expressions for Joining and Complex Relationships".

Using TopLink Workbench

To use joining in a relationship mapping, use this procedure:

Select the mapped attribute in the Navigator. Its properties appear in the Editor.
Click the General tab. The General tab appears.

Figure 37-1 General Tab, Use Joining Option

Description of "Figure 37-1 General Tab, Use Joining Option"

To use joining with this relationship, select the Use Joining option.