DROP TABLE IF EXISTS items;
CREATE TABLE items (
name VARCHAR(255),
color SET('black') NULL,
KEY color_index(color)
) DEFAULT CHARSET=utf8mb4;
INSERT INTO items VALUES ('hat', '');
INSERT INTO items VALUES ('t-shart', NULL);
INSERT INTO items VALUES ('parka', 'black');
SELECT mroonga_command('index_column_diff --table items#color_index --name index');
mroonga_command('index_column_diff --table items#color_index --name index')
[]
SELECT * FROM items WHERE color = '';
name	color
hat	
t-shart	
DROP TABLE items;
