1CREATE TABLE parent ( 2id INT NOT NULL, 3PRIMARY KEY (id) 4) ENGINE=InnoDB; 5CREATE TABLE child ( 6id INT, 7parent_id INT, 8FOREIGN KEY (parent_id) 9REFERENCES parent(id) 10ON UPDATE SET NULL 11ON DELETE SET NULL 12) ENGINE=InnoDB; 13INSERT INTO parent VALUES (1),(2); 14INSERT INTO child VALUES (1,1),(2,2); 15connection node_2; 16DELETE FROM parent WHERE id = 1; 17SELECT parent_id IS NULL FROM child WHERE id = 1; 18parent_id IS NULL 191 20connection node_1; 21SELECT parent_id IS NULL FROM child WHERE id = 1; 22parent_id IS NULL 231 24UPDATE parent SET id = 3 WHERE id = 2; 25SELECT parent_id IS NULL FROM child WHERE id = 2; 26parent_id IS NULL 271 28connection node_2; 29SELECT parent_id IS NULL FROM child WHERE id = 2; 30parent_id IS NULL 311 32connection node_1; 33DROP TABLE child; 34DROP TABLE parent; 35