Relationships in Salesforce

Relationships:
Relationships are used to  establish connection between two or more Objects.By these Relationships to avoid Data Redundancy and to achieve Integrity.

Relationships associate objects with other objects. For example, a relationship can link a custom object to standard object in a related list, such as linking a custom object called Bugs to cases to track product defects associated with customer cases. 

Navigation:

Setup.....>Build....>Create.....>Objects....>Open the Existing Object.....>Fields and Relations....>Select New

Step1--->Select the Relationship type

Step2--->Enter the Field details

Step3--->Establish to the Field-Level-security

Step4--->Add the fields to Page layouts. 

Types of Relationships:

3 Types of Relationships

1.One-To-Many                               2.One-To-One                             3.Many-To-Many

• Master-Detail                       ---->It is also called the                 ----->It is also called              
• Lookup                                        Hierarchy Relation                          Junction Object.

Example:

Chatter Objects

Diagram showing the relationships between the Chatter objects

The following diagram shows the relationships between the major Chatter objects.

• A feed item is an entry in the feed, such as a change to a record that's being followed, an updated post, or a user status change.
• All feed items have a ParentId, which is either:
  • the record that is changed
  • the user who received the post