First solution : CASE
SELECT id
FROM oc_products
WHERE product_description LIKE '%my search keywords%'
OR product_description LIKE '%my%'
OR product_description LIKE '%search%'
OR product_description LIKE '%keywords%'
ORDER BY CASE WHEN product_description LIKE '%my search keywords%' THEN 0
WHEN product_description LIKE '%my search&' THEN 1
WHEN product_description LIKE '%my&' THEN 2
WHEN product_description LIKE '%search&' THEN 3
WHEN product_description LIKE '%keywords&' THEN 4
END DESC
Second solution : listing conditions in ORDER BY
SELECT id
FROM oc_products
WHERE product_description LIKE '%my search keywords%'
OR product_description LIKE '%my%'
OR product_description LIKE '%search%'
OR product_description LIKE '%keywords%'
ORDER BY product_description LIKE '%my search keywords%' DESC
, product_description LIKE '%my search&' DESC
, product_description LIKE '%my&' DESC
, product_description LIKE '%search&' DESC
, product_description LIKE '%keywords&' DESC