SELECT isbn ,  count(*) FROM Books_Order GROUP BY isbn
Show all book isbns and the numbers of orders for each.
create table Client
(IdClient CHAR(10) PRIMARY KEY,
 Name VARCHAR(25) NOT NULL,
 Address VARCHAR(60) NOT NULL,
 NumCC CHAR(16) NOT NULL);
create table Orders
(IdOrder CHAR(10) PRIMARY KEY,
 IdClient CHAR(10) NOT NULL REFERENCES Client on delete cascade,
 DateOrder DATE,
 DateExped DATE);
create table Author
( idAuthor NUMBER PRIMARY KEY,
  Name VARCHAR(25));
create table Book
(ISBN CHAR(15) PRIMARY KEY,
Title VARCHAR(60) NOT NULL,
Author CHAR(4) NOT NULL,
PurchasePrice NUMBER(6,2) DEFAULT 0,
SalePrice NUMBER(6,2) DEFAULT 0);
create table Author_Book
(ISBN CHAR(15),
Author NUMBER,
CONSTRAINT al_PK PRIMARY KEY (ISBN, Author),
CONSTRAINT BookA_FK FOREIGN KEY (ISBN) REFERENCES `Book`(ISBN) on delete cascade,
CONSTRAINT Author_FK FOREIGN KEY (Author) REFERENCES `Author`(idAuthorA));
create table Books_Order(
ISBN CHAR(15),
IdOrder CHAR(10),
amount NUMBER(3) CHECK (amount >0),
CONSTRAINT lp_PK PRIMARY KEY (ISBN, idOrder),
CONSTRAINT Book_FK FOREIGN KEY (ISBN) REFERENCES `Book`(ISBN) on delete cascade,
CONSTRAINT pedido_FK FOREIGN KEY (IdOrder) REFERENCES `Orders`(IdOrder) on delete cascade);
INSERT into Client values ('0000001','James Smith', 'Picadilly 2','1234567890123456');
INSERT into Orders values ('0000001P','0000001', DATE('01/12/2011'),DATE('03/12/2011')
INSERT into Author values (1,'Jane Austin');
INSERT into Book values ('8233771378567', 'Pride and Prejudice', '2008', 9.45, 13.45);
INSERT into Author_Book values ('8233771378567',1);
INSERT into Books_Order values ('8233771378567','0000001P', 1);
INSERT INTO Client VALUES [('0000001', 'James Smith', 'Picadilly 2', '1234567890123456'), ('0000002', 'Laura Jones', 'Holland Park 13', '1234567756953456')]
INSERT INTO Orders VALUES [('0000001P', '0000001', None, None), ('0000002P', '0000001', None, None)]
INSERT INTO Author VALUES [(1, 'Jane Austin'), (2, 'George Orwell')]
INSERT INTO Book VALUES [('8233771378567', 'Pride and Prejudice', '2008', 9.45, 13.45), ('1235271378662', '1984', '2009', 12.5, 19.25)]
INSERT INTO Author_Book VALUES [('8233771378567', 1), ('1235271378662', 2)]
INSERT INTO Books_Order VALUES [('8233771378567', '0000001P', 1), ('5463467723747', '0000001P', 2)]