MySQL添加聯接子查詢來計數

Question

我有兩張桌子的貸款和書本。

通過此查詢，我通過計算Book_ID來計算從貸款中借出的大部分圖書：

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

現在，我想在這里從Book表中添加Book標題。 我有Book_ID作為貸款表中的外鍵。 我不太確定如何將這個查詢放在一起。

這是我嘗試過的但沒有結果：

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

由於您已經加入了另一個表，所以您的列名含糊不清，請嘗試為其賦予別名：

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;