Relationship in Salesforce

A Relationship is a way in which two or more people or things are connected with each other. The way they connected will be of different types likewise in salesforce there are 6 different types of relationships in salesforce.

• Master-Detail relationship
• Look Up relationship
• Many-to-Many relationship
• Self-relationship
• External relationship
• Hierarchical relationship 

Master-Detail relationship :

Master-Detail relationship is a type of relationship, one object acts as a master and the other acts as a detail object. In other words, this relationship acts as a parent-child relationship. We use this type of relationship when we want to bound two objects tightly or closely dependent on each other.

Important Points Regarding Master-Detail relationship

• In Master-Detail Relationship the “child object” or “detail object” must have a parent.
• Roll-up Summary fields can be established.
• Records can be re-parented.
• Standard objects can not be a detailed object
• Maximum 2 Master-Detail Relationships can be created for an Object.

Look Up relationship :

Look Up relationship is a type of relationship in which that if one gets deleted then the related object will not get deleted.

Important Points Regarding look Up Relationship

• When a parent’s record gets deleted, the child remains in existence.
• We cannot create a roll-up summary field in a lookup relationship.
• The relationship is optional.
• No impact on Security.

Many-to-Many relationships:

In Many-to-Many relationships, records of particular objects are linked to multiple records of different objects and vice versa. There is no such field as a many-to-many relationship in Salesforce, we can create a many-to-many relationship by creating two master-detail relationships with a common object. 

Important Points Regarding Many-to-Many relationships Relationship

• A Junction Object is used to create Many-Many Relationships.
• A junction object can also be called a Join Object.

Self-relationship:

Self-relationship simply means creating a relationship with itself. In this, we can relate an object with itself by look-up. 

External relationship:

In External lookup relationships, it allows a relationship to be formed between two external objects. It supports standard look-up relationships that use 18 characters Salesforce Id for the association.

Hierarchical relationship:

This unique relationship can only be used on the user object and is designed to create a hierarchy of users.