MySQL Получите последние дубликаты рядов
SELECT
t1.primary_id,
t1.duplicate_id,
t1.data1,
t1.data2
FROM
table_name t1
LEFT JOIN table_name t2
ON (t1.duplicate_id = t2.duplicate_id AND t1.primary_id < t2.primary_id)
WHERE
t2.primary_id IS NULL
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