查询未完成 - MYSQL

Question

到目前为止我的查询：

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，我的查询是根据CD_no和购买的输入生成的，查找日期是该特定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可能在两个不同的日期可能具有完全相同的最大购买量，因此应该根据CD编号显示两个日期。

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

来自以下输入：

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字段的数量，因此上面仅对purchase_date进行分组。

在其他RDBMS中，您可以使用子查询：

SELECT a1.CD_NO, a1.purchase_date, a2.TotalSalesByDate
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
ORDER BY a1.CD_NO

<击>

编辑：根据您的更新，您应该可以使用类似的内容：

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);

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 |