Object relationships

You can relate an object to other objects in Salesforce. For example, relating a custom object Expense to custom object Project. With this relation, you'll know which expense record is used for which project. Project, in this example, will be considered as the parent object, and Expense as a child object. From the record-level perspective, one parent can have many children, while the child can only have one parent. To build this relationship from the child object, create a Lookup Relationship or Master-Detail Relationship field to the parent object.

There are three types of object relationships in Salesforce, which are as follows:

• Master-Detail Relationship
• Lookup Relationship
• Hierarchical Relationship

The following table compares the Master-Detail Relationship and Lookup Relationship:

Hierarchical Relationship is a special Lookup relationship available for the user object only. It lets users use a lookup field to associate one user with another, which does not directly or indirectly refer to itself. For example, you can create a custom Hierarchical Relationship field to store each user's reporting manager.