Question

我有两张桌子贷款和书。

通过这个查询，我通过计算Book_ID来计算贷款中大部分借出的书籍：

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

现在我想从Book表中添加Book title。我在贷款表中将Book_ID作为外键。我不太确定如何将这个查询放在一起。

这是我尝试但没有结果：

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

由于您已加入另一个表，因此您拥有不明确的列名，请尝试为它们添加别名：

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;

Mysql添加join子查询来计算

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