SELECT *
FROM (

SELECT p.products_image, d.products_name, p.products_model, d.products_id, d.products_description, p.abra_sc_id,
CASE nz.nl_id
WHEN 31
THEN 'checked'
ELSE 'Null'
END AS checkbox_checked,
CASE nz.v_akci
WHEN 1
THEN 'checked'
ELSE 'Null'
END AS v_akci,
nh.pole_tabulky1,
nh.pole_tabulky2
FROM products p
INNER JOIN products_description d ON d.products_id = p.products_id
LEFT JOIN newsletters_zbozi nz ON nz.id_zbozi = p.products_id
AND nz.nl_id =31
LEFT JOIN newsletters_zbozi_hlavni nh on nh.id_zbozi = nz.id_zbozi
) AS zbozi
WHERE checkbox_checked = 'checked'