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create table categories (id_cat serial primary key, name varchar(50));
create table products (id_pr serial primary key, name_pr varchar(50), ed_izmer varchar(50), cena int, quantity int, nds int, id_cat_pr int references categories(id_cat));
create table sales (number_p_p serial primary key, date_sales timestamp, id_pr_sales int references products(id_pr), quantity_sales int);
insert into categories values (1, 'Молочные'), (2, 'Мукомольные');
insert into products values (1, 'Молоко', 'литр', 100, 50, 10, 1), (2, 'Творог', 'грамм', 120, 25, 18, 1), (3, 'Мука в/сорт', 'килограмм', 80, 100, 10, 2), (4, 'Мука п/сорт', 'килограмм', 90, 90, 10, 2);
insert into sales values (1, '2022.04.01', '1', 5), (2, '2022.04.01', '2', 5), (3, '2022.04.01', '3', 8), (4, '2022.04.01', '1', 2), (5, '2022.04.05', '4', 15), (6, '2022.04.05', '3', 5);