Question

我在我的数据库中创建了两个视图，每个视图都包含由'br_engagement'在不同时间段内排序的人员列表。我想计算从旧时期到新时期的等级变化。我认为如果我可以在视图中存储变量，这将是很容易的，但是我面临着如何执行查询的挑战，我计算排名的变化时，我只能在{{找到的会话变量中获取它{3}}

这是我能够为新时期创造的前10名的视图：

+---------+----------------------+
|  name   | total_br_engagements |
+---------+----------------------+
| Person1 |                97553 |
| Person2 |                73576 |
| Person3 |                15245 |
+---------+----------------------+

为了添加排名，我会SELECT @rank := @rank +1 AS rank, name, total_br_engagements FROM (SELECT * FROM top10current) t1, (SELECT @rank :=0)t2

现在的问题是如何从一个视图（top10old）到一个新视图（top10current）找到排名的变化。我的第一次尝试是：

select @rank:=@rank+1 as rank, old.oldrank, (old.oldrank-rank), new.name,  new.total_br_engagements 
    from ((select name, total_br_engagements from top10current) t1, (select @rank:=0) t2)  new
left join (
    SELECT @rn:=@rn+1 as `oldrank`, name, side, party, total_br_posts, total_br_engagements
    from (select name, side, party, total_br_posts, total_br_engagements from top10old) t01, (select @rn:=0) t02) old 
on new.name=old.name

但是在'新左连接（SELECT @rn：= @ rn + 1为oldrank，名称'附近出现错误。

有更简单的方法可以做到这一点，还是我走在正确的轨道上？

更新：我修改了代码以使用new_rank作为我当前前十名的名称，但我得到了同样的错误。我还在第二个表中删除了一些不必要的变量名。这是新代码：

select @rank:=@rank+1 as rank, old.oldrank, (old.oldrank-rank), new_rank.name, new_rank.total_br_engagements 
    from (
        (select name, total_br_engagements from top10current) t1, (select @rank:=0) t2)  new_rank
left join (
    SELECT @rn:=@rn+1 as `oldrank`, name, side, party, total_br_posts, total_br_engagements
        from (select name, total_br_engagements from top10old) t01, (select @rn:=0) t02) old 
on new_rank.name=old.name

Answer 1

这是我对您的SQL代码的最好尝试，如果我错了，请不要咬T_T

SELECT    @rank := @rank + 1       AS `rank`, 
          old.oldrank              AS `oldrank`, 
          old.oldrank - @rank       AS `rankchange`, 
          new.name                 AS `name`, 
          new.total_br_engagements AS `total_br_engagements` 
FROM      ( 
          ( 
                 SELECT name, 
                        total_br_engagements 
                 FROM   top10current) AS t1, 
          ( 
                 SELECT @rank := 0) AS new) 
LEFT JOIN 
          ( 
                 SELECT @rn := @rn + 1 AS `oldrank`, 
                        `t2`.`name`, 
                        `t2`.`side`, 
                        `t2`.`party`, 
                        `t2`.`total_br_posts`, 
                        `t2`.`total_br_engagements` 
                 FROM   ( 
                               SELECT `name`, 
                                      `side`, 
                                      `party`, 
                                      `total_br_posts`, 
                                      `total_br_engagements` 
                               FROM   top10old) AS t2, 
                        ( 
                               SELECT @rn := 0) AS old
                        ) AS t3
ON        `new`.`name` = `old`.`name`;

Answer 2

基于@LFlare的回答。

SELECT    @rank := @rank + 1       AS `rank`, 
          old.oldrank              AS `oldrank`, 
          (old.oldrank- @rank) as `change`,
          `new`.name                 AS `name`, 
          `new`.total_br_engagements AS `total_br_engagements` 
FROM      ( 
          ( 
                 SELECT name, 
                        total_br_engagements 
                 FROM   top10current) AS `new`, 
          ( 
                 SELECT @rank := 0) AS t1) 
LEFT JOIN 
          ( 
                 SELECT @rn := @rn + 1 AS `oldrank`, 
                        `old`.`name`, 
                        `old`.`total_br_engagements` 
                 FROM   ( 
                               SELECT `name`, 
                                      `total_br_engagements` 
                               FROM   top10old) AS old2, 
                        ( 
                               SELECT @rn := 0) AS t2
                        ) AS old
ON        `new`.`name` = `old`.`name`

计算MySQL中排名的变化

2 个答案: