(
-- нормальные товары
SELECT product.name, price.value
FROM product 
JOIN price ON product.id=price.product_id and price.id_pricelist=1
WHERE product.broken=0 and product.damaged=0 and price.value>0
) 
UNION
(
-- треснутые товары
SELECT product.name, price.value
FROM product 
JOIN price ON product.id=price.product_id and price.id_pricelist=2
WHERE product.broken=1 and price.value>0
)
UNION
(
-- товары со значительными повреждениями
SELECT product.name, price.value
FROM product 
JOIN price ON product.id=price.product_id and price.id_pricelist=2
WHERE product.damaged=1 and price.value>0
)
LIMIT 30

CREATE TABLE product_markdown (
  id int(11) UNSIGNED NOT NULL AUTO_INCREMENT,
  id_product int(11) UNSIGNED NOT NULL,
  broken tinyint(4) NOT NULL COMMENT 'Разбит',
  damaged tinyint(4) NOT NULL COMMENT 'Повреждения',
  PRIMARY KEY (id),
  UNIQUE INDEX uk_art (product_id),
)
ENGINE = INNODB
COMMENT = 'Причины уценки товара';

FROM product 
LEFT JOIN price
ON product.id=price.id AND (
    (product.id_markdown IS NULL AND price.id_pricelist=1)
     OR (product.id_markdown=>1 AND price.id_pricelist=2)
    )