SOQL and SOSL Reference

Introduction to SOQL and SOSL
Salesforce Object Query Language (SOQL)
Typographical Conventions in This Document
Quoted String Escape Sequences
Reserved Characters
Alias Notation
SOQL SELECT Syntax
SOQL SELECT Examples
SOQL SELECT Functions
Relationship Queries
Understanding Relationship Names
Using Relationship Queries
Understanding Relationship Names, Custom Objects, and Custom Fields
Understanding Query Results
null Values in Lookup Relationships and Outer Joins
Identifying Parent and Child Relationships
Understanding Relationship Fields and Polymorphic Fields
Understanding Relationship Query Limitations
Using Relationship Queries with History Objects
Using Relationship Queries with Data Category Selection Objects
Using Relationship Queries with the Partner WSDL
Change the Batch Size in Queries
SOQL Object Limits and Limitations
Syndication Feed SOQL and Mapping Syntax
Location-Based SOQL Queries
Considerations for Querying Currency Data Using SOQL
Salesforce Object Search Language (SOSL)
PDF

Using Relationship Queries with History Objects

Custom objects and some standard objects have an associated history object that tracks changes to an object record. You can use SOQL relationship queries to traverse a history object to its parent object.

For example, the following query returns every history row for Foo__c and displays the name and custom fields of Foo:

1SELECT OldValue, NewValue, Parent.Id, Parent.name, Parent.customfield__c 
2FROM foo__history

This example query returns every Foo object row together with the corresponding history rows in nested subqueries:

1SELECT Name, customfield__c, (SELECT OldValue, NewValue FROM foo__history) 
2FROM foo__c