Can we create Junction object with one master-detail and one lookup field? What will be its security configuration in case Lookup relationship field is created first?

  • Great question. I also wondered if there are any security implications.
    – DevelBase2
    Mar 13, 2022 at 11:09
  • 1
    For the first question, yes you can. I don't understand the second question. Do you mean when creating the junction object fields, or when creating a junction object record? For the former, what security issues could you have? For the latter, a Master Detail field is always required, so must be set when first creating the record.
    – Phil W
    Mar 13, 2022 at 11:51
  • @PhilW I want to know if the org-wide default will be ControlledByParent or Public Read/Write Mar 13, 2022 at 12:46
  • Just set it how you want it for the Lookup. Master Detail children are always Controlled by Parent.
    – Phil W
    Mar 13, 2022 at 13:57

1 Answer 1


Answer to your first questions is "Yes" you can have a junction object by using one parent as M-D and another as Lookup.

For second question sharing setting of your child object would be Controlled by parent and it can't be changed to anything else.

Depending on your use case you can expand or restrict sharing setting on child object from "Sharing Setting" option at master detail relationship field.

  • Allows users with at least Read access to the Master record to create, edit, or delete related Detail records.
  • Allows users with at least Read/Write access to the Master record to create, edit, or delete related Detail records.

Remember you cant create a child record without linking master object record

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