DROP TABLE IF EXISTS users;
CREATE TABLE users (
name VARCHAR(255),
role ENUM("guest") NULL,
KEY role_index(role)
) DEFAULT CHARSET=utf8mb4;
INSERT IGNORE INTO users VALUES ("newbie", "");
INSERT INTO users VALUES ("alice", NULL);
INSERT INTO users VALUES ("bob", "guest");
SELECT mroonga_command("index_column_diff --table users#role_index --name index");
mroonga_command("index_column_diff --table users#role_index --name index")
[]
SELECT * FROM users WHERE role = "";
name	role
newbie	
alice	
DROP TABLE users;
