SELECT
PI.product_id,
F1.id AS file_id,
F1.path AS file,
(
SELECT
PI1.alt
FROM
`cscart_products__images` PI1
WHERE
PI1.original_file_id = F1.id
) AS file_alt,
F2.id AS big_file_id,
F2.path AS big_file,
(
SELECT
PI2.alt
FROM
`cscart_products__images` PI2
WHERE
PI2.watermark_big_file_id = F2.id
) AS big_file_alt,
F3.id AS small_file_id,
F3.path AS small_file,
(
SELECT
PI3.alt
FROM
`cscart_products__images` PI3
WHERE
PI3.watermark_small_file_id = F3.id
) AS small_file_alt
FROM
`cscart_products__images` AS `PI`
LEFT JOIN `files` AS `F1` ON `F1`.`id` = `PI`.`original_file_id`
LEFT JOIN `files` AS `F2` ON `F2`.`id` = `PI`.`watermark_big_file_id`
LEFT JOIN `files` AS `F3` ON `F3`.`id` = `PI`.`watermark_small_file_id`
WHERE
`PI`.`product_id` = 26376