DELETE t2.*
FROM the_table t1
INNER JOIN the_table t2
ON t2.non_unique_column = t1.non_unique_column
AND t2.id > t1.id;
DELETE t2.*
FROM the_table t1
INNER JOIN the_table t2
ON t2.non_unique_column = t1.non_unique_column
AND t2.id > t1.id;