Using Relationship Queries with the Partner WSDL

The partner WSDL doesn’t contain the detailed type information that’s available in the enterprise WSDL which you need for a relationship SOQL query. You must first execute a describeSObjects() call, and from the results, gather the information you need to create your relationship query:

• The relationshipName value for one-to-many relationships, for example, in an Account object, the relationship name for the asset child is Assets.
• The reference fields available for the relevant object, for example, whoId, whatId, or ownerId on a Lead, Case, or custom object.

For an example of using the partner WSDL with relationship queries, see the examples on developer.salesforce.com (requires login).