What is the difference between Lookup relationship & Master detail relationship?

Look up relationship:

  • Parent field on child can be required or optional choice.
  • No impact on security and access.
  • If we delete parent record then child records are not deleted.
  • No limit to number of layers.
  • Up to 25 allowed for an object.
  • We can change parent object for child object.
  • Roll-up summary field is not allowed.

Master – Detail Relationship:

  • Parent field on child is required.
  • Access to parent determines access to children.
  • Deleting parent automatically delete children.
  • Limited number of layers.
  • Up to 2 allowed for an object.
  • We can’t change the parent object for child object once create. The only way is killing the both objects.
  • Roll-up summary field is allowed.