Mam takie tabele :
create table usr(
id serial primary key,
user_name varchar(15) unique not null,
pass_word varchar(100) not null,
email varchar(150) unique not null,
enabled boolean not null
);
create table category(
id serial primary key,
category varchar(100) unique not null
);
create table expense(
id serial primary key,
expense_date date not null,
amount decimal(10,2) not null,
comment text,
user_id integer not null,
category_id integer not null,
payment_method_id integer not null,
payee_id integer,
constraint fk_user foreign key(user_id) references usr(id),
constraint fk_category foreign key(category_id) references category(id),
constraint fk_payment_method foreign key (payment_method_id) references payment_method,
constraint fk_payee foreign key (payee_id) references payee(id),
check (amount>=0)
);
Jak zrobić selekta który wybierze sume wydatków po kategorii między danymi datami i wstawi 0 jeśli dany user nie miał wydatków w danej kategorii?
Dodam że korzystam z postgresa