Oracle 18c

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CREATE TABLE "USER" ( id NUMBER PRIMARY KEY );
CREATE TABLE user_backup ( id NUMBER PRIMARY KEY );
CREATE TABLE user_address(
Id          Number PRIMARY KEY,
User_id     Number CONSTRAINT name_of_previous_fk_to_user_backup REFERENCES user_backup ( id ),
Address_Id  Number
);
ALTER TABLE user_address ADD CONSTRAINT user_address__id__fk
  FOREIGN KEY (user_id) REFERENCES "USER" ( id );
ALTER TABLE user_address DROP CONSTRAINT name_of_previous_fk_to_user_backup;