Sestavení dotazu se SELECT UNION..

Tabulka OBJEDNAVKY:
id_objednavka, id_zakaznik, doprava, doprava_cena, celkem_bez_dph, celkem_s_dph, celkem_poplatek, celkova_cena, nazev, ic, dic, jmeno, prijmeni, email, ulice, cislo, obec, psc, zeme, ulice_dod, cislo_dod, obec_dod, psc_dod, zeme_dod, telefon, poznamka,zak_cislo, datum, stav, jazyk, web, id_dopravce, id_dopravce_stat, datum2, id_platba, platba, typ_karty, platba_hash.

Tabulka ZAKAZNICI:
id,uz_jm, heslo, nazev, ic, dic, jmeno, prijmeni, email, ulice, cislo, obec, psc, zeme, id_stat_fakturacni, ulice_dod, cislo_dod, obec_dod,psc_dod, zeme_dod, id_stat_dodaci, dodaci_adr_jina, telefon, poznamka, icq, platebni_lhuta, druh, datum, aktivni.

SELECT 
o.jmeno AS jmeno,
o.prijmeni AS prijmeni,
o.email AS email,
count(o.id_objednavka) AS pocet_objednavek,
sum(o.celkem_bez_dph) as celkem_bez_dph 
FROM objednavky o 
JOIN zakaznici z ON z.email = o.email 
AND z.uz_jm = 'bez_registrace'
GROUP BY o.email

UNION
						
SELECT 
o.jmeno AS jmeno,
o.prijmeni AS prijmeni,
o.email AS email,
count(o.id_objednavka) AS pocet_objednavek,
sum(o.celkem_bez_dph) as celkem_bez_dph 
FROM objednavky o 
JOIN zakaznici z ON z.id = o.id_zakaznik 
AND z.uz_jm <> 'bez_registrace'
GROUP BY z.id 
ORDER BY celkem_bez_dph DESC
LIMIT 10
") or die(err(1)); 

SELECT 
o.jmeno AS jmeno,
o.prijmeni AS prijmeni,
o.email AS email,
count(o.id_objednavka) AS pocet_objednavek,
sum(o.celkem_bez_dph) as celkem_bez_dph,
IF(z.uz_jm='bez_registrace', z.email, z.id) AS udaj

FROM objednavky o 
JOIN zakaznici z ON z.id = o.id_zakaznik 
IF(z.uz_jm='bez_registrace', GROUP BY z.email, GROUP BY z.id) 
ORDER BY celkem_bez_dph DESC
LIMIT 10