mysql - 如何在 SQL 查询中按客户名称合并总成本？

Question

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;

我需要将 borrowerName 的总成本合并起来，但真的不确定如何做？

Answer 1

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