I am getting #1066 - Not unique table/alias: 'pf' error here - mysql

Question

SELECT COUNT(DISTINCT `product_id`) AS `total`
FROM(
SELECT DISTINCT `p`.`product_id`
FROM oc_category_path cp
LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id)
LEFT JOIN oc_product_filter pf ON (p2c.product_id = pf.product_id)
LEFT JOIN oc_product p ON (pf.product_id = p.product_id)
LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id)
LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id)
INNER JOIN `oc_product_filter` AS `pf` ON `p2c`.`product_id` = `pf`.`product_id`
WHERE IF( `p`.`quantity` > 0, 7, `p`.`stock_status_id` ) IN(7)
AND `p`.`date_available` <= NOW()
AND `p`.`status` = '1'
AND `cp`.`path_id` = '452'
AND `pf`.`filter_id` IN(241)
AND pd.language_id = '1'
AND p.status = '1'
AND p.date_available <= NOW()
AND p2s.store_id = '0'
AND cp.path_id = '452'
AND pf.filter_id IN (241)
) AS `tmp`

Answer 1

This line...
LEFT JOIN oc_product_filter pf ON (p2c.product_id = pf.product_id)
... shares a table alias with this line ...
INNER JOIN `oc_product_filter` AS `pf` ON `p2c`.`product_id` = `pf`.`product_id`
That can't happen. So give the second one a different alias...
SELECT COUNT(DISTINCT product_id) total
FROM
( SELECT DISTINCT p.product_id
FROM oc_category_path cp
LEFT
JOIN oc_product_to_category p2c
ON p2c.category_id = cp.category_id
JOIN oc_product_filter pf
ON pf.product_id = p2c.product_id
JOIN oc_product p
ON p.product_id = pf.product_id
JOIN oc_product_description pd
ON pd.product_id = p.product_id
JOIN oc_product_to_store p2s
ON p2s.product_id = p.product_id
JOIN oc_product_filter pf2 -- <-- changed
ON pf.product_id = p2c.product_id
WHERE IF(p.quantity > 0, 7, p.stock_status_id ) IN(7)
AND p.date_available <= NOW()
AND p.status = 1
AND cp.path_id = 452
AND pf.filter_id IN(241)
AND pd.language_id = 1
AND p.status = 1
AND p.date_available <= NOW()
AND p2s.store_id = 0
AND cp.path_id = 452
AND pf2.filter_id IN(241) -- <-- changed
) tmp;