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Hi Vajrala,
Salesforce supports 2 kinds of relationships like Master Detail and Lookup. They are both one-to-many relationship, and they are both defined from the many-to-one side, that is from a child to a parent. They can be made one-to-one relationship by adding validation rules, or maybe triggers to enforce the one-to-one nature, i.e. only one child is allowed.
Junction objects are used to create many to many relationships between objects. If you take the Recruiting application example, you can see that a Position can be linked to many Candidates, and a Candidate can apply for different Positions. To create this data model you need a third object "Job Application" that links the 2.
So you'd create a lookup field for both Position and Candidate object on the "Job Application" object. This will establish many to many relationship between Position and Candidate via the "Job Application" object known as the junction object.
Fore more information, read this article http://wiki.developerforce.com/page/A_Deeper_look_at_SOQL_and_Relationship_Queries_on_Force.com.
Anup
All Answers
Hi Vajrala,
Salesforce supports 2 kinds of relationships like Master Detail and Lookup. They are both one-to-many relationship, and they are both defined from the many-to-one side, that is from a child to a parent. They can be made one-to-one relationship by adding validation rules, or maybe triggers to enforce the one-to-one nature, i.e. only one child is allowed.
Junction objects are used to create many to many relationships between objects. If you take the Recruiting application example, you can see that a Position can be linked to many Candidates, and a Candidate can apply for different Positions. To create this data model you need a third object "Job Application" that links the 2.
So you'd create a lookup field for both Position and Candidate object on the "Job Application" object. This will establish many to many relationship between Position and Candidate via the "Job Application" object known as the junction object.
Fore more information, read this article http://wiki.developerforce.com/page/A_Deeper_look_at_SOQL_and_Relationship_Queries_on_Force.com.
Anup
Hi,
Check this link for detailed explaination .
http://shivasoft.in/blog/salesforce/deep-drive-in-junction-object-create-many-to-many-relationship-in-salesforce/
A custom object with two master-detail relationships. Using a custom junction object, you can model a “many-to-many” relationship between two objects. For example, you may have a custom object called “Bug” that relates to the standard case object such that a bug could be related to multiple cases and a case could also be related to multiple bugs.
Creating the many-to-many relationship consists of:
Creating the junction object.
Creating the two master-detail relationships.
Customizing the related lists on the page layouts of the two master objects.
Customizing reports to maximize the effectiveness of the many-to-many relationship.
Creating the Junction Object
To create the junction object:
From Setup, click Create | Objects.
Click New Custom Object.
In the custom object wizard, consider these tips specifically for junction objects:
Name the object with a label that indicates its purpose, such as BugCaseAssociation.
For the Record Name field, it is recommended that you use the auto-number data type.
Do not launch the custom tab wizard before clicking Save. Junction objects do not need a tab.
Creating the Two Master-Detail Relationships
To create the two master-detail relationships:
Verify that the two objects you want to relate to each other already exist. For example, you may want to relate the standard case object to a custom bug object.
On the junction object, create the first master-detail relationship field. In the custom field wizard:
Choose Master-Detail Relationship as the field type.
Select one of the objects to relate to your junction object. For example, select Case.
The first master-detail relationship you create on your junction object becomes the primary relationship. This affects the following for the junction object records:
Look and feel: The junction object's detail and edit pages use the color and any associated icon of the primary master object.
Record ownership: The junction object records inherit the value of the Owner field from their associated primary master record. Because objects on the detail side of a relationship do not have a visible Owner field, this is only relevant if you later delete both master-detail relationships on your junction object.
Division: If your organization uses divisions to segment data, the junction object records inherit their division from their associated primary master record. Similar to the record ownership, this is only relevant if you later delete both master-detail relationships.
Select a Sharing Setting option. For master-detail relationship fields, the Sharing Setting attribute determines the sharing access that users must have to a master record in order to create, edit, or delete its associated detail records.
For the Related List Label that will display on the page layout of the master object, do not accept the default. Change this to use the name of the other master object in your many-to-many relationship. For example, change this to Bugs so users will see a Bugs related list on the case detail page.
On the junction object, create the second master-detail relationship. In the custom field wizard:
Choose Master-Detail Relationship as the field type.
Select the other desired master object to relate to your junction object. For example, select Bug.
The second master-detail relationship you create on your junction object becomes the secondary relationship. If you delete the primary master-detail relationship or convert it to a lookup relationship, the secondary master object becomes primary.
Select a Sharing Setting option. For master-detail relationship fields, the Sharing Setting attribute determines the sharing access that users must have to a master record in order to create, edit, or delete its associated detail records.
For the Related List Label that will display on the page layout of the master object, do not accept the default. Change this to use the name of the other master object in your many-to-many relationship. For example, change this to Cases so users will see a Cases related list on the bug detail page.
"Job Application" object in Recruitng App is NOT a junction object as Junction object needs 2 Master Detail relationship (According to the documentation).
In above mentioned example it has 2 lookups , one on Position and other on Candidate.
https://help.salesforce.com/HTViewHelpDoc?id=relationships_manytomany.htm
http://www.jitendrazaa.com/blog/salesforce/deep-drive-in-junction-object-create-many-to-many-relationship-in-salesforce/
I have one junction object - suppose Test. And it creates two master relationship betweeen Account and Contact. All the relationship and records are presented in my QA environment. We have several recordsd like one contact associates with two account and vice versa. I have loaded my Account and Contact in DEV pro landscape using data loder, but as of now the relationship records are not present unless and util I load Junction Object Test. I have exported the data from Junction object but I dont know how to create the mapping files and to which I need to associate my ID's.
Account have external id - Account__c
Help me to load the data in DEV for Junction object
Thanks body
that was very useful
This answers are useful..
Also, "A junction object is a custom object with two Master-Detail relationships." Does this mean is it a master AND a child so that it's A >B>C?? Because it can't be that this junctino object has 2 masters. What am I not understanding here?
Yes,it is possible by realting the case(standard object) and application user(custom object which you created) by creating a junction object( In this case,Let's say Issues(custom object). Define a master-detail relationship field between case and issues, application user and issues as well.
For more clear understanding,Check out this vedio.
https://youtu.be/Jy5JZ42XN6Q
Hope this is helpful.
Thanks,
Mounika.
In fact, I've built several SFDC orgs where the junction object uses only lookup relationships. You give up cascading deletes and rollup fields, but you get the ability to link to a third object...plus some interesting security features that aren't possible with the inherited ownership/visibility of master/detail.
https://www.sfdc-lightning.com/2018/11/what-is-junction-object-in-salesforce.html
http://www.jitendrazaa.com/blog/salesforce/deep-drive-in-junction-object-create-many-to-many-relationship-in-salesforce/
https://www.u-techrides.com/2020/05/sfdc-many-to-many-object-relationship.html (https://www.u-techrides.com/2020/05/sfdc-many-to-many-object-relationship.html)
From technical point of view, all of the 3 scenarios can play as juction between two objects.
Junction object is nothing but a custom object, it contains two master detail relationship, for example , if we want to book a ticket for flight to USA or any other place but the location of the city or state is in diffrent object and account details is on other object so we create one custom object called junction object to get all the details in single object.
Best practices for the creation of Junction Object in Salesforce is
The first master-detail created on the junction object is known as the primary master
The second master-detail created on the junction object is known as the secondary master.
Whoever is the owner of the primary master will be the owner of corresponding child records.
If we delete any one of the master records the corresponding child records will get deleted too.
Junction objects are fascinating connectors in Salesforce! Your post brilliantly explains their purpose and creation process. As someone planning a Long distance moving (https://nestmovingstorage.com/long-distance-moving/) of data, I found your insights invaluable for streamlining relationships between objects. Thanks for shedding light on this crucial concept!