1 answer
Any of those can be called a junction object. A junction object simply forms a many to many relationship between two objects. I would say 99% of the time you would make that a master-detail for both objects in the junction. However there are always exceptions to the rules. For example, if your junction object had additional information that you wanted to keep if one of the parents were deleted then you would not want to make that a master-detail.Examples: Master-Detail for both:
- If you look at the CaseTeamMember or AccountTeamMember object, this is a simple junction object between the Case/Account and a User. It also has some additional information on it such as the type the member is. In this case it does not make sense to keep the member object around if either the Case/Account or the User are deleted and creating one without either serves no purpose. So making them both master-detail makes the most sense
Lookup for both / some:
- In my opinion this is the toughest to find a good use for. Lets say you had a Case and a Group object and you wanted to pair them together with a Contact to make a CaseGroupMember junction object. While it may make some sense to make all of the master-detail, lets say (for argument sake) that you wanted to keep the CaseGroupMember object around for forensic work or you have some process that you then alert your Contact or Case owner if the Group is deleted that they need to do something. In this case you'd want to make some of these a lookup or all of them a look up so that your data hangs around.
