DROP DATABASE IF EXISTS mnoziny2;
CREATE DATABASE IF NOT EXISTS mnoziny2;
USE mnoziny2;

CREATE TABLE T1 (x INT, y VARCHAR(5));
CREATE TABLE T2 (x INT, y VARCHAR(5)); 

INSERT INTO T1(x,y) VALUES(1,'A');
INSERT INTO T1(x,y) VALUES(2,'B');
INSERT INTO T1(x,y) VALUES(NULL,'C');
INSERT INTO T1(x,y) VALUES(4,NULL);
INSERT INTO T1(x,y) VALUES(NULL,NULL);

INSERT INTO T2(x,y) VALUES(1,'A');
INSERT INTO T2(x,y) VALUES(3,'D');
INSERT INTO T2(x,y) VALUES(NULL,'C');
INSERT INTO T2(x,y) VALUES(4,NULL);
INSERT INTO T2(x,y) VALUES(NULL, NULL);