Одним не обойтись, а двумя можно всё грохнуть )
Это для одного языка
Если языков больше - надо запрос подшаманить
Если описания с пустыми HTML тегами тоже считать пустыми, можно вместо t0.description = '' отбирать по длине описания CHAR_LENGTH(t0.description) < 20
DELETE `t01`,`t02`,`t03`,`t04`,`t05`,`t06`,`t07`,`t08`,`t09`,`t10`,`t11`,`t12`,`t13`,`t14`,`t15`,`t16`,`t17`,`t18`,`t19`
FROM `oc_product_description` AS `t0`
LEFT JOIN `oc_product` AS `t01` ON(`t0`.`product_id` = `t01`.`product_id`)
LEFT JOIN `oc_product_attribute` AS `t02` ON(`t0`.`product_id` = `t02`.`product_id`)
LEFT JOIN `oc_product_discount` AS `t03` ON(`t0`.`product_id` = `t03`.`product_id`)
LEFT JOIN `oc_product_filter` AS `t04` ON(`t0`.`product_id` = `t04`.`product_id`)
LEFT JOIN `oc_product_image` AS `t05` ON(`t0`.`product_id` = `t05`.`product_id`)
LEFT JOIN `oc_product_option` AS `t06` ON(`t0`.`product_id` = `t06`.`product_id`)
LEFT JOIN `oc_product_option_value` AS `t07` ON(`t0`.`product_id` = `t07`.`product_id`)
LEFT JOIN `oc_product_recurring` AS `t08` ON(`t0`.`product_id` = `t08`.`product_id`)
LEFT JOIN `oc_product_related` AS `t09` ON(`t0`.`product_id` = `t09`.`product_id`)
LEFT JOIN `oc_product_related` AS `t10` ON(`t0`.`product_id` = `t10`.`related_id`)
LEFT JOIN `oc_product_reward` AS `t11` ON(`t0`.`product_id` = `t11`.`product_id`)
LEFT JOIN `oc_product_special` AS `t12` ON(`t0`.`product_id` = `t12`.`product_id`)
LEFT JOIN `oc_product_to_category` AS `t13` ON(`t0`.`product_id` = `t13`.`product_id`)
LEFT JOIN `oc_product_to_download` AS `t14` ON(`t0`.`product_id` = `t14`.`product_id`)
LEFT JOIN `oc_product_to_layout` AS `t15` ON(`t0`.`product_id` = `t15`.`product_id`)
LEFT JOIN `oc_product_to_store` AS `t16` ON(`t0`.`product_id` = `t16`.`product_id`)
LEFT JOIN `oc_review` AS `t17` ON(`t0`.`product_id` = `t17`.`product_id`)
LEFT JOIN `oc_coupon_product` AS `t18` ON(`t0`.`product_id` = `t18`.`product_id`)
LEFT JOIN `oc_url_alias` AS `t19` ON(CONCAT('product_id=',`t0`.`product_id`) = `t19`.`query`)
WHERE `t0`.`description = '';
DELETE `pd`
FROM `oc_product_description` AS `pd`
LEFT JOIN `oc_product` AS `p` ON(`pd`.`product_id` = `p`.`product_id`)
WHERE `p`.`product_id` IS NULL;