Parent to Child – Relationship Queries in SOQL

Understanding relationships between different objects is important to managing Salesforce data effectively. One of the most common and powerful relationships is the Parent-to-Child relationship, which enables you to organize and structure data in a way that reflects real-world scenarios. This relationship type helps in building robust data models that support complex business processes. A parent-to-child relationship query in SOQL is used to retrieve child records associated with a parent record. In this chapter, we will look at how you can use this query to fetch data from standard as well as custom objects.

What is a Parent-to-Child Relationship Query?

A Parent-to-Child relationship query in Salesforce allows you to retrieve data from related objects where the parent object has a one-to-many relationship with the child object. This means that for each record in the parent object, there can be multiple related records in the child object. Parent-to-child relationship queries allow you to efficiently retrieve data from both the parent and child objects in a single SOQL query, making it convenient to access related records. 

Example:

In the case of an Account object (parent) and a Contact object (child) the Account can have multiple associated Contacts. Using a Parent-to-Child relationship query, you can retrieve an Account and all related Contacts in a single query.

For Standard Objects

There are some pre-defined relationships in Salesforce between many standard objects. Such as:

• Account (Parent) → Contact (Child)
• Opportunity (Parent) → Opportunity Product (Child)
• Case (Parent) → Case Comment (Child)

Example SOQL Query:

List<Account> AccountData = [SELECT Id, Name, Industry, AnnualRevenue, NumberOfEmployees, (SELECT FirstName, LastName FROM Contacts) FROM Account]

For Custom Objects

For custom objects, the query format is similar but requires the use of the __r suffix for the child relationship name:

Example of Custom Objects:

1. Project (Parent) → Task (Child)
2. Department (Parent) → Employee (Child)
3. Bank (parent) → Branch (child)

SELECT Bank_Name__c, (SELECT Branch_Id__c, Name, State__c FROM Branches__r) FROM Bank__c

This custom query will fetch:

• The Bank_Name__c field from the Bank__c object (parent)
• A subquery that selects Branch_Id__c, Name, and State__c fields from the Branches__r object (child) that are related to each Bank__c record
• The __r suffix is used for the child relationship name for custom objects.

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