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SELECT version();
| version() |
|---|
| 8.0.30 |
CREATE TABLE tablename (
a INT(10) NOT NULL,
b INT(10) NOT NULL,
UNIQUE ((LEAST(a, b)), (GREATEST(a, b)))
);
INSERT INTO tablename (`a`, `b`) VALUES ('1', '2');
INSERT INTO tablename (`a`, `b`) VALUES ('2', '1');
Duplicate entry '1-2' for key 'tablename.functional_index'