Как объединить общую стоимость по имени клиента в запросе SQL?

Question

Моя попытка ниже:

SELECT BookLoan.borrowerName, Book.cost
FROM BookLoan
JOIN Book ON BookLoan.bookTitle = Book.title
JOIN Borrower ON BookLoan.borrowerName = Borrower.name;

Мне нужно объединить общую стоимость на borrowerName, но действительно не знаете, как?

Answer 1

Группировка по сумме.

SELECT BookLoan.borrowerName
, SUM(Book.cost) AS TotalCost
FROM BookLoan 
LEFT JOIN Book 
  ON Book.title = BookLoan.bookTitle
LEFT JOIN Borrower 
  ON Borrower.name = BookLoan.borrowerName
GROUP BY BookLoan.borrowerName
ORDER BY BookLoan.borrowerName;

Answer 2

SELECT BookLoan.borrowerName, SUM(Book.cost) as TotalCost
FROM BookLoan
JOIN Book ON BookLoan.bookTitle = Book.title
JOIN Borrower ON BookLoan.borrowerName = Borrower.name
GROUP BY BookLoan.borrowerName