select distinct jmeno from zakaznik join vypujcka on vypujcka.zakaznik_id = zakaznik.id;

select distinct jmeno from zakaznik left join vypujcka on vypujcka.zakaznik_id = zakaznik.id where vypujcka.kniha_id is not null;

select 1 as pocetknih, jmeno from zakaznik where (select count (*) from vypujcka where id = zakaznik_id) = 1
union
select 2 as pocetknih, jmeno from zakaznik where (select count (*) from vypujcka where id = zakaznik_id) = 2;

select count (*) as pocetknih, jmeno from zakaznik inner join vypujcka on vypujcka.zakaznik_id = zakaznik.id group by jmeno having count (*) in (1,2);

select jmeno from zakaznik where jmeno like 'p%' and id in (select zakaznik_id from vypujcka);


select jmeno from zakaznik where jmeno like 'p%'
intersect
select distinct jmeno from zakaznik join vypujcka on vypujcka.zakaznik_id = zakaznik.id;


select jmeno from zakaznik
where id not in
(select zakaznik_id from ((select zakaznik.id as zakaznik_id, kniha.id from zakaznik cross join kniha)
minus
(select zakaznik_id, kniha_id from vypujcka)));



//Kolikrat byla ktera kniha pujcena
//Jaky knihy na p byli pujceny
//