INSERT INTO PROFESOR(cod_pro, nombre) VALUES('JR', 'Juan Ruiz');
-- Fails here, constraint is INITIALLY IMMEDIATE
INSERT INTO PROFESOR(cod_pro, nombre) VALUES('JR', 'Javier Pérez');
ROLLBACK; -- Don't save the first insertion

-- Change constraint to be INITIALLY DEFERRED
ALTER TABLE profesor DROP PRIMARY KEY CASCADE KEEP INDEX;
ALTER TABLE profesor ADD CONSTRAINT cp_prof PRIMARY KEY(cod_pro) INITIALLY DEFERRED DEFERRABLE;
-- Because we used CASCADE to DROP the primary key constraint,
-- we need to restore the FOREIGN KEY in docencia
ALTER TABLE docencia
	ADD CONSTRAINT ca_doc_prof
	FOREIGN KEY(cod_pro) REFERENCES profesor(cod_pro) INITIALLY IMMEDIATE DEFERRABLE;

INSERT INTO PROFESOR(cod_pro, nombre) VALUES('JR', 'Juan Ruiz');
INSERT INTO PROFESOR(cod_pro, nombre) VALUES('JR', 'Javier Pérez');
-- Fails here, constraint is INITIALLY DEFERRED
COMMIT;

-- Restore constraint to initial setting
ALTER TABLE profesor DROP PRIMARY KEY CASCADE KEEP INDEX;
ALTER TABLE profesor ADD CONSTRAINT cp_prof PRIMARY KEY(cod_pro) INITIALLY IMMEDIATE DEFERRABLE;
ALTER TABLE docencia ADD CONSTRAINT ca_doc_prof FOREIGN KEY(cod_pro) REFERENCES profesor(cod_pro) INITIALLY IMMEDIATE DEFERRABLE;