Удаление дубликатов строк с помощью sql

Я пытаюсь удалить дубликаты строк из моей таблицы mysql. Я пробовал несколько запросов, но продолжаю получать эту ошибку: #1093 - You can't specify target table 'usa_city' for update in FROM clause

Таблица выглядит так:

usa_city
--------
id(pk)
id_state
city_name

И запросы, которые я устал были:

DELETE FROM usa_city
WHERE id NOT IN
(
SELECT MIN(id)
FROM usa_city
GROUP BY city_name, id_state
)

И:

DELETE
FROM usa_city
WHERE usa_city.id IN

-- List 1 - all rows that have duplicates
(SELECT F.id
FROM usa_city AS F
WHERE Exists (SELECT city_name, id_state, Count(id)
FROM usa_city
WHERE usa_city.city_name = F.city_name
   AND usa_city.id_state = F.id_state
GROUP BY usa_city.city_name, usa_city.id_state
HAVING Count(usa_city.id) > 1))
AND usa_city.id NOT IN

-- List 2 - one row from each set of duplicate
(SELECT Min(id)
FROM usa_city AS F
WHERE Exists (SELECT city_name, id_state, Count(id)
FROM usa_city
WHERE usa_city.city_name = F.city_name
   AND usa_city.id_state = F.id_state
GROUP BY usa_city.city_name, usa_city.id_state
HAVING Count(usa_city.id) > 1)
GROUP BY city_name, id_state);

Спасибо заранее.

0
задан Christopher Stephenson 19 December 2011 в 20:18
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