I\'ve a table CustomizationSet with the columns:
customization_set_guid (which is a non-nullable guid and also the primary key) creator_account_guid and a fe
I got the same error, and it was due to the fact that the foreign key already existed. What you want is just to add the constraint:
ALTER TABLE Registration ADD CONSTRAINT idx_Registration_CustomizationSet FOREIGN KEY (customization_set_guid) REFERENCES CustomizationSet(customization_set_guid);