DROP TABLE IF EXISTS ids;
CREATE TABLE ids (
id INT
) DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
INSERT INTO ids (id) values (1), (1);
ALTER TABLE ids ADD UNIQUE INDEX (id);
ERROR 23000: Can't write, because of unique constraint, to table 'ids'
SHOW CREATE TABLE ids;
Table	Create Table
ids	CREATE TABLE `ids` (
  `id` int DEFAULT NULL
) ENGINE=Mroonga DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
SELECT * FROM ids;
id
1
1
DROP TABLE ids;
