mysql - 如何在SQL查询中按客户名称组合总成本？

我的尝试如下：

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

我需要按borrowerName组合总费用，但真的不确定如何？

最佳答案

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