CREATE TABLE tableB(
ID		SERIAL,
Number		INT4
);

CREATE TABLE tableA (
ID		SERIAL,
Description	TEXT,
tableB_id	INT4 REFERENCES tableB(ID)
		ON DELETE RESTRICT
);


INSERT INTO tableB(number) VALUES (1111);
INSERT INTO tableB(number) VALUES (2222);
INSERT INTO tableB(number) VALUES (3333);

INSERT INTO tableA(Description, tableB_id) VALUES ('First one', 1);
INSERT INTO tableA(Description, tableB_id) VALUES ('Second one', 2);
INSERT INTO tableA(Description, tableB_id) VALUES ('Third one', 3);

