SELECT `id`,COUNT(*) as `cnt`
FROM `table`
GROUP BY `поле с повторами!`
HAVING `cnt` > 1

DELETE FROM mytable WHERE id IN (
SELECT id FROM  (
SELECT id,id_author,id_genre FROM mytable WHERE id_author 
IN (SELECT id_author FROM (
SELECT id_author,COUNT(id_author) AS idaut FROM mytable GROUP BY  id_author
)
AS tt1
WHERE idaut > 1 )
AND
id_genre IN (
SELECT id_genre 	FROM (
SELECT id_genre,COUNT(id_genre) AS idgenr FROM mytable GROUP BY  id_genre
)
AS tt2
WHERE idgenr > 1
)
) AS ttt
)

AND

id NOT IN
(SELECT mid FROM (
SELECT MIN(id) as mid,id_author,id_genre FROM mytable GROUP BY id_author,	id_genre
) AS tttt
)

DELETE FROM `test2`
WHERE `id_gente` IN (
    SELECT `id_gente` FROM (
        SELECT `id_gente` FROM `test2`
        GROUP BY `id_gente` 
        HAVING COUNT(*) > 1
    ) AS `t1`
)
AND `id` NOT IN (
    SELECT `id` FROM (
        SELECT `id` FROM `test2`
        GROUP BY `id_gente`
        HAVING COUNT(*) > 1
    ) AS `t2`
)