Question

是sql的新手，无法找到查询示例。

所以，我有一张桌子：

bought ( customer_name, month, year, quantity, product_name )

我想找到在特定月份EX销售最多的产品。 2014年4月

让我们说：

| Jan | April | 2014 | 7 | Watches |
| Ron | April | 2014 | 4 |  Rings  |
| Jan | April | 2014 | 4 |  Rings  |

现在我有：

SELECT product_name
FROM bought
WHERE month_bought = 'April' AND year_bought = 2014 AND 
           quantity_buy >= all (SELECT quantity_buy
                                FROM bought 
                                WHERE month_bought = 'April' AND year_bought = 2014
                               );

我不确定是否/在哪里使用GROUP BY作为product_name。

Answer 1

您需要汇总，因为多个客户可以购买相同的产品。这反过来建议HAVING而不是WHERE：

SELECT product_name
FROM bought b
WHERE month_bought = 'April' AND year_bought = 2014 
GROUP BY product_name
HAVING SUM(quantity_buy) >= all (SELECT SUM(b2.quantity_buy)
                                 FROM bought b2
                                 WHERE b2.month_bought = b.month_bought AND 
                                       b2.year_bought = b.year_bought
                                 GROUP BY product_name
                               );

还有其他方式来表达此查询。这似乎与你想写的最接近。

Answer 2

如果没有进一步的测试，它应该是这样的：

SELECT product_name

FROM bought

WHERE month_bought = 'April' AND year_bought = 2014 AND 

       sum(quantity_buy) = (SELECT max(sum(quantity_buy)) FROM bought 

       WHERE month_bought = 'April' AND year_bought = 2014 group by  product_name)
group by product_name;

如果以相同数量销售，这将返回多个产品。

添加组SQL的总和

2 个答案: