CREATE TABLE client (
	id SERIAL PRIMARY KEY,
	nom VARCHAR(50),
	solde INTEGER );
CREATE TABLE ligne (
	id SERIAL PRIMARY KEY,
	numero VARCHAR(20),
	tarif FLOAT,
	id_client INTEGER REFERENCES client );
CREATE TABLE appel (
	id SERIAL PRIMARY KEY,
	debut TIMESTAMP,
	fin TIMESTAMP,
	id_ligne_appelant INTEGER REFERENCES ligne,
	id_ligne_appele INTEGER REFERENCES ligne );
