Mysql添加连接子查询来计数

Question

我有两张表Loan and Book。

与此查询我用数Book_ID数从贷款最贷款的书：

select Book_ID, count(Book_ID) as Count 
from Loan 
group by Book_ID 
order by Count desc; 

现在我想从书表中添加书名这里。我在贷款表中有Book_ID作为外键。我不太清楚如何将这个查询放在一起。

这是我尝试过，但没有结果：

select Book_ID, count(Book_ID) as Count, Book.Title 
from Loan, Book 
where Loan.Book_ID = Book.Book_ID 
group by Book_ID 
order by Count desc; 

Answer 1

你有ambigious列名，因为你已经加入到另一个表，尽量给他们一个别名：

select Book.Book_ID, count(Book.Book_ID) as Count, Book.Title 
from Loan, Book 
where Loan.Book_ID = Book.Book_ID 
group by Book.Book_ID 
order by Count desc;