Question

表格中的数据将每天添加一个抓取工具。所以第一个条目应该每天排名第一。但是因为爬虫可以在2倍的时间内爬行产品。显示下一行具有相同的名称。如果这是真的那么它需要与前一行具有相同的排名。

这是我到目前为止所做的事情：

    SELECT a.product_ranking_id, a.Productinfo, a.Date, 
    (
      SELECT index(Productinfo)
      From ProductRanking as b
      Where a.Date = b.Date
    ) as Rank
    From ProductRanking as a

结束结果

+------------------------+--------------+------------+------+
| Table:  ProductRanking |              |            |      |
+------------------------+--------------+------------+------+
| product_ranking_id     | Productinfo  | Date       | Rank |
+------------------------+--------------+------------+------+
|                        | product 1    | 01-01-2018 | 1    |
+------------------------+--------------+------------+------+
|                        | product 1    | 01-01-2018 | 1    |
+------------------------+--------------+------------+------+
|                        | product 2    | 01-01-2018 | 2    |
+------------------------+--------------+------------+------+
|                        | product 3    | 01-01-2018 | 3    |
+------------------------+--------------+------------+------+
|                        | product 445  | 01-01-2018 | 4    |
+------------------------+--------------+------------+------+
|                        | product 3    | 02-01-2018 | 1    |
+------------------------+--------------+------------+------+
|                        | product 89   | 02-01-2018 | 2    |
+------------------------+--------------+------------+------+
|                        | product 89   | 02-01-2018 | 2    |
+------------------------+--------------+------------+------+

解决方案：

在Gordon Linoff的帮助下，我找到了一个解决方案。这就是为什么我标记他的答案。如果它可以更好，总是欢迎..

SELECT *,(@i := if(a.Productinfo != b.Productinfo, 
                if(a.date = b.date, @i + 1,@i := 1),   @i)   ) as Rank
From
    productrank as a
    left join productrank as b on b.product_ranking_id = a.product_ranking_id -1
    Cross join (SELECT @i := 1) params
;

Answer 1

我想你想要：

select pr.*,
       (@rn := if(@pd = concat_ws(' ', productinfo, date), @rn + 1,
                  if(@pd := concat_ws(' ', productinfo, date), 1, 1)
                 )
       ) as rank
from (select pr.*
      from ProductRanking pr
      order by Productinfo, Date
     ) pr cross join
     (select @pd := '', @rn := 0) params;

在旧版本的MySQL中，子查询不是必需的。您可以在外部查询中order by。

编辑：

假设product_ranking_id包含顺序ID：

select pr.*,
       (@rn := if(@p = productinfo, @rn + 1,
                  if(@p := productinfo, 1, 1)
                 )
       ) as rank
from (select pr.*
      from ProductRanking pr
      order by Productinfo, product_ranking_id
     ) pr cross join
     (select @p := '', @rn := 0) params;

MySql，设置每天的行排名

1 个答案: