The used SELECT statements have a different number of columns

select * from ( (select 'clanek' as kat, clanky.*, clanky_kategorie.id as kategorieid, clanky.id as clanekid from clanky, clanky_kategorie where kategorie = clanky_kategorie.id and publikovano = 1 and homepage = 1 and date<'2019-06-27 03:56:04') union all (select 'recenze' as kat, recenze.*, recenze_kategorie.id as kategorieid, recenze.id as clanekid from recenze, recenze_kategorie where kategorie = recenze_kategorie.id and publikovano = 1 and homepage = 1 and date<'2019-06-27 03:56:04') union all (select 'zavod' as kat, zavody.*, zavody_kategorie.id as kategorieid, zavody.id as clanekid from zavody, zavody_kategorie where kategorie = zavody_kategorie.id and publikovano = 1 and homepage = 1 and date<'2019-06-27 03:56:04') ) as data order by data.`date` desc limit 4