connection node_2;
connection node_1;
CREATE TABLE t1 (f1 INT DEFAULT NULL, UNIQUE KEY i1 (f1)) ENGINE=InnoDB;
INSERT INTO t1 VALUES (NULL);
INSERT INTO t1 VALUES (NULL);
connection node_2;
SELECT COUNT(*) = 2 FROM t1;
COUNT(*) = 2
1
SELECT f1 IS NULL FROM t1;
f1 IS NULL
1
1
DROP TABLE t1;