Total sum of price and quantity in oracle - sql

Question

I have a problem. I need to calculate a total sum of order in my DB. I have 3 tables:
CREATE TABLE Potrawa(
id_potrawy INT CONSTRAINT Potrawa_PK PRIMARY KEY,
Nazwa VARCHAR2(150) NOT NULL,
Cena NUMBER(6,2) NOT NULL, **(PRICE)**
Opis VARCHAR(100)
);
CREATE TABLE Zamowienie(
id_zamowienia INT CONSTRAINT Zamowienie_PK PRIMARY KEY,
Ilosc INT, **(QUANTITY)**
Data DATE,
Ocena INT CONSTRAINT Ocena_Zamowienie_CHECK CHECK (Ocena IN (1, 2, 3, 4, 5)),
klient_id INT CONSTRAINT Zamowienie_Klient_FK REFERENCES Klient(id_klient),
pracownik_id INT CONSTRAINT Zamowienie_Pracownik_FK REFERENCES Pracownik(id_pracownik),
potrawy_id INT CONSTRAINT Zamowienie_Menu_FK REFERENCES Potrawa(id_potrawy),
typ_zamowienia_id INT CONSTRAINT Zamowienie_Typ_FK REFERENCES Typ_zamowienia(id_typ_zamowienia)
);
CREATE TABLE Menu(
restauracja_id INT NOT NULL CONSTRAINT Menu_Restauracje_FK REFERENCES Restauracja(id_restauracja),
potrawa_id INT NOT NULL CONSTRAINT Menu_Potrawa_FK REFERENCES Potrawa(id_potrawy),
CONSTRAINT Menu_PK PRIMARY KEY(restauracja_id, potrawa_id),
rodzaj_menu_id INT CONSTRAINT Menu_Rodzaj_Menu_FK REFERENCES Rodzaj_menu(id_rodzaj_menu)
);
I want to write a query that show me sum of each order. I wrote sth like this, but it's not working. Sum is not that I expect.
select distinct z.id_zamowienia as "zamowienie", z.potrawy_id as "Potrawa", p.nazwa as "Nazwa potrawy", z.ilosc as ILOSC,
count(*) over(partition by z.potrawy_id, z.id_zamowienia) * p.cena AS "CENA"
from potrawa p, menu m, zamowienie z
where p.id_potrawy = m.potrawa_id and m.potrawa_id = z.potrawy_id
Can someone give me tip how to fix it or how can I do it in another way (PARTITION BY is obligatory).

Answer 1

First of all it's always better to use proper join syntax. Do you want to find sum(Ilosc) instead of count(*) for that partition?
select distinct
z.id_zamowienia as "zamowienie",
z.potrawy_id as "Potrawa",
p.nazwa as "Nazwa potrawy",
z.ilosc as ILOSC,
sum(Ilosc) over(partition by z.potrawy_id, z.id_zamowienia) * p.cena AS "CENA"
from
potrawa p
inner join menu m on p.id_potrawy = m.potrawa_id
inner join zamowienie z and m.potrawa_id = z.potrawy_id