Thank’s everyone for your attention.
If anybody will need to query database with two postmeta, here is the code
SELECT p.*
, CASE WHEN m1.meta_value=0 OR m1.meta_value IS NULL
THEN m2.meta_value
ELSE m1.meta_value
END meta_value
FROM aka_v_posts p
LEFT JOIN aka_v_postmeta m1 ON p.id=m1.post_id AND m1.meta_key='_wpsc_special_price'
LEFT JOIN aka_v_postmeta m2 ON p.id=m2.post_id AND m2.meta_key='_wpsc_price'
WHERE post_title LIKE '%32%'
AND post_type="wpsc-product"
ORDER BY aka_v_posts.post_date DESC
The thing to keep in mind (at least I was doing it wrong) is that you need to check for meta_values before the FROM keyword, to select those meta_values.