Music Shop
Существующие таблицы create table Albums(album_id int, album_name varchar(20), singer_name varchar(20), primary key(album_id)) create table Singers(singer_id int, singer_name varchar(20), genre varchar(20), primary key(singer_id)) create table Sales(singer_id int, album_id int, primary key(singer_id, album_id), foreign key(album_id) references Albums, foreign key(singer_id) references Singers) alter table Sales add count_of_sold_albums int create table Shop(singer_id int, album_id int, available int, primary key(album_id), foreign key(album_id) references Albums) create table Studios(singer_id int, album_id int, label_name varchar(20), primary key(album_id), foreign key(album_id) references Albums) create table Singles(singer_id int, album_id int, single_name varchar(20), foreign key(singer_id) references Singers, foreign key(album_id) references Albums) Существующие отношения 1:1 1:М М:М