如何每月获得最畅销的商品

Question

我想获得每个月最畅销的商品/产品。我尝试使用GROUP BY函数，但是我的问题是如何每个月只获得一种产品。

O(NlogN)

此外，如何在mysql中使用SELECT MONTHNAME(date), product, SUM(quantity) FROM mytable GROUP BY MONTHNAME(date), product 函数？我想通过使用我每月只能得到一种产品？

这就是我想要得到的：

Answer 1

SELECT
        month, n, product, quantity
    FROM
      ( SELECT  @prev := '', @n := 0 ) init
    JOIN
      ( SELECT  @n := if(MONTHNAME(date) != @prev, 1, @n + 1) AS n,
                @prev := MONTHNAME(date),
                MONTHNAME(date) AS month, product, SUM(quantity) AS quantity
            FROM  mytable
            GROUP BY
                MONTHNAME(date), product
            ORDER BY
                MONTHNAME(date) ASC,
                SUM(quantity) DESC
      ) x
    WHERE  n <= 1
    ORDER BY  month, n