我的SQL每次返回第一行，

Question

SELECT p.Producttype, pp.ProductID, r.Date1, r.Date2 
FROM customers AS c 
INNER JOIN orders AS r ON c.Cusid = r.Cusid 
INNER JOIN temporary AS temp ON r.Cusid = temp.Cusid 
INNER JOIN products AS pp ON pp.ProductID = temp.ProductID 
INNER JOIN Producttypes AS p ON p.Producttypeid = pp.Producttypeid 
WHERE temp.Cusid = '23' 
GROUP BY pp.ProductID 

请帮助我不知道自己能做什么，该查询返回每次第一行到日期1和date2

Answer 1

这是MySQL的一个已知的问题列。 它将允许组由没有未分组字段的任意聚合函数。

它返回其默认行为组，通过以外的所有领域的第一聚集。 看到这个：Why does MySQL allow "group by" queries WITHOUT aggregate functions?和Any reason for GROUP BY clause without aggregation function?

删除Group By条款，你应该没问题。

SELECT p.Producttype, pp.ProductID, r.Date1, r.Date2 
FROM customers AS c 
INNER JOIN orders AS r ON c.Cusid = r.Cusid 
INNER JOIN temporary AS temp ON r.Cusid = temp.Cusid 
INNER JOIN products AS pp ON pp.ProductID = temp.ProductID 
INNER JOIN Producttypes AS p ON p.Producttypeid = pp.Producttypeid 
WHERE temp.Cusid = '23' 
--GROUP BY pp.ProductID -->This should be removed as it causes to returne the first of each other field while keeping ProductID distinct in the returned table.