DELETE FROM pmd_listings c1

WHERE EXISTS (
    SELECT *
    FROM pmd_listings c2
    WHERE c2.id <> c1.id
        AND c2.friendly_url = c1.friendly_url
        AND c2.www = c1.www
        AND c2.listing_zip = c1.listing_zip
)

AND c1.id <> (
    SELECT MIN(c2.id)
    FROM pmd_listings c2
    WHERE c2.friendly_url = c1.friendly_url
        AND c2.www = c1.www
        AND c2.listing_zip = c1.listing_zip
)