每年哪款手机销量高？

Question

我在 mysql 中有一个表。如何编写查询以找到销量最高的手机名称（每年 Sold_out 的最高数量）

--------------------------------------------
Phone      Sold_out      Month      Year
--------------------------------------------
iphone      3            Jan-15     2015
iphone      10           Feb-15     2015
samsung     4            March-15   2015
Lava        14           June-16    2016
Lenova      8            July-16    2016
Lenova      10           Sep-16     2016 
Motorola    8            Jan-17     2017
Nokia       7            Jan-17     2017
Nokia       3            Feb-17     2017
--------------------------------------------

我需要的结果是

-----------------------------
year      Phone      sales
-----------------------------
2015      iphone     13
2016      lenova     18
2017      Nokia      10
-----------------------------

Answer 1

在派生表中，总销售额按 (year,phone) 组合计算。计算出总销售额后，应确定每年的所有顶部行（按销售额排名 = 1）。通过使用相关子查询和有子句，从每个组（年份）中识别第一行并显示为最终输出。

SELECT year,phone, sales_per_year
  FROM
      (
      SELECT year,phone,SUM(sold_out) AS sales_per_year
        FROM sales
      GROUP BY year,phone          
      ) o
 GROUP BY year,phone
 HAVING (
           SELECT COUNT(*)
             FROM 
                   (
                      SELECT year,phone,SUM(sold_out) AS sales_per_year
                        FROM sales
                      GROUP BY year,phone                          
                    ) i  
           WHERE i.year = o.year             
             AND i.sales_per_year > o.sales_per_year 
          ) < 1          
ORDER BY year,phone,sales_per_year DESC         

检查 sql fiddle 链接 http://sqlfiddle.com/#!9/ff096e/14