查询未完成 - MYSQL

Question

我的查询到目前为止：

SELECT CD_no, purchasedate, COUNT(*) mostsales
FROM Sales A
GROUP BY CD_no, purchasedate
HAVING COUNT(*) =
        (SELECT MAX(mostsales)
         FROM
            (SELECT CD_no, purchasedate, COUNT(*) AS mostsales
                FROM Sales
            GROUP BY CD_no, purchasedate) B
            WHERE CD_no = A.CD_no)

到目前为止，我的查询来自CD_no和购买的输入，发现日期具有该特定CD的最大销售额。 但是，这仅为每个CD编号返回一个值。 但是，CD_no可能在两个不同日期具有完全相同的最大购买量，因此应该针对CD号显示两个日期。

当前输出：

CD_NO           mostsales
1             2011-12-30
2             2012-03-22
3             2012-04-24

期望的输出：

CD_NO           mostsales
1             2011-12-30
2             2012-03-22
3             2012-04-24
3             2012-04-22

从以下输入：

CD_NO         purchase_date
1              2011-12-30
1              2011-12-30
1              2011-12-29
1              2011-12-28
2              2012-03-22
2              2012-03-22
2              2012-03-21
3              2012-04-24
3              2012-04-24
3              2012-04-22
3              2012-04-22              
3              2012-04-21

Answer 1

听起来你需要添加一个聚合函数：

 
 
 
  
  SELECT CD_NO, purchase_date, Count(purchase_date) totalSales FROM Artist GROUP BY purchase_date ORDER BY CD_NO
 
  

MySQL允许您限制 GROUP BY的字段数，因此上面仅对 purchase_date分组。

在其他RDBMS中，您可以使用子查询：

SELECT a1.CD_NO, date_format(a1.purchase_date, '%Y-%m-%d') MostSales
FROM Artist a1
INNER JOIN
(
    SELECT count(purchase_date) TotalSalesByDate, purchase_date
    FROM Artist
    GROUP BY purchase_date
) a2
   on a1.purchase_date= a2.purchase_date
group by a1.CD_NO, a1.purchase_date
having max(TotalSalesByDate) = (select max(Total) totalsales
                                 from
                                 (
                                    SELECT cd_no, purchase_date, Count(purchase_date) Total
                                    FROM Artist a1
                                    GROUP BY cd_no, purchase_date
                                 ) src
                                 where a1.cd_no = src.cd_no
                                 GROUP BY cd_no);

编辑：根据您的更新，您应该能够使用类似于此的内容：

| CD_NO |  MOSTSALES |
----------------------
|     1 | 2011-12-30 |
|     2 | 2012-03-22 |
|     3 | 2012-04-22 |
|     3 | 2012-04-24 |

请参阅SQL Fiddle with Demo

结果：

 | CD_NO | MOSTSALES | ---------------------- | 1 | 2011-12-30 | | 2 | 2012-03-22 | | 3 | 2012-04-22 | | 3 | 2012-04-24 |