sql使用Count（*）函数

Question

我正在使用Microsoft Access 2013和 我想在每家咖啡馆找到订单数量，但显示的数字是错误的。 这是我的代码：

SELECT Avg(Feedback.RatingForExperience) AS caferating,
      Count(tblOrder_Product.ProductCode) AS cafesales, Feedback.cafeid
FROM tblOrder_Product, Feedback
GROUP BY Feedback.cafeid;

请帮帮我，谢谢。

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Answer 1

如评论中所述，您需要将表格加在一起。下面是SQL。

SELECT Avg(Feedback.RatingForExperience) AS caferating,
  Count(tblOrder_Product.ProductCode) AS cafesales, Feedback.cafeid
FROM tblOrder_Product INNER JOIN Feedback ON tblOrder_Product.OrderCode = Feedback.OrderCode
GROUP BY Feedback.cafeid;

或者

SELECT Avg(Feedback.RatingForExperience) AS caferating,
  Count(tblOrder_Product.ProductCode) AS cafesales, Feedback.cafeid
FROM tblOrder_Product LEFT JOIN Feedback ON tblOrder_Product.OrderCode = Feedback.OrderCode
GROUP BY Feedback.cafeid;