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CREATE TABLE tablename (
`sid` INTEGER,
`id` INTEGER,
`amount` INTEGER
);
INSERT INTO tablename
(`sid`, `id`, `amount`)
VALUES
('1', '12', '30'),
('2', '45', '30'),
('3', '45', '50'),
('4', '78', '80'),
('5', '78', '70');
UPDATE tablename t1
INNER JOIN (
SELECT MIN(sid) sid, id
FROM tablename
GROUP BY id
) t2 ON t2.id = t1.id AND t2.sid < t1.sid
INNER JOIN tablename t3 ON t3.sid = t2.sid
SET t1.amount = t3.amount;
SELECT * FROM tablename;
| sid | id | amount |
|---|---|---|
| 1 | 12 | 30 |
| 2 | 45 | 30 |
| 3 | 45 | 30 |
| 4 | 78 | 80 |
| 5 | 78 | 80 |