Apex Developer Guide

Apex Developer Guide
Release Notes
Getting Started with Apex
Writing Apex
Data Types and Variables
Control Flow Statements
Classes, Objects, and Interfaces
Working with Data in Apex
Working with sObjects
Data Manipulation Language
SOQL and SOSL Queries
Working with SOQL and SOSL Query Results
Accessing sObject Fields Through Relationships
Understanding Foreign Key and Parent-Child Relationship SOQL Queries
Working with SOQL Aggregate Functions
Working with Very Large SOQL Queries
Using SOQL Queries That Return One Record
Improve Performance by Avoiding Null Values
Working with Polymorphic Relationships in SOQL Queries
Using Apex Variables in SOQL and SOSL Queries
Querying All Records with a SOQL Statement
SOQL For Loops
sObject Collections
Dynamic Apex
Apex Security and Sharing Model
Custom Settings
Document Your Apex Code
Running Apex
Debugging, Testing, and Deploying Apex
Apex Reference
Appendices
PDF

Understanding Foreign Key and Parent-Child Relationship SOQL Queries

The SELECT statement of a SOQL query can be any valid SOQL statement, including foreign key and parent-child record joins. If foreign key joins are included, the resulting sObjects can be referenced using normal field notation. For example:

1System.debug([SELECT Account.Name FROM Contact
2              WHERE FirstName = 'Caroline' WITH USER_MODE].Account.Name);

Additionally, parent-child relationships in sObjects act as SOQL queries as well. For example:

1for (Account a : [SELECT Id, Name, (SELECT LastName FROM Contacts)
2                  FROM Account
3                  WHERE Name = 'Acme'
4                  WITH USER_MODE]) {
5     Contact[] cons = a.Contacts;
6}
7
8//The following example also works because we limit to only 1 contact
9for (Account a : [SELECT Id, Name, (SELECT LastName FROM Contacts WITH USER_MODE LIMIT 1)
10                  FROM Account
11                  WHERE Name = 'testAgg']) {
12     Contact c = a.Contacts;
13}