在 mySQL 和 VIEW 创建中分配排名

Posted 2023-02-26

【中文标题】在 mySQL 和 VIEW 创建中分配排名

【英文标题】：Assiging rank in mySQL and VIEW creation

【发布时间】：2013-04-29 13:37:30

【问题描述】：

我有一张名为积分榜的表格，其中包含每支球队的积分、净胜球和进球数。这是表结构和数据。

CREATE TABLE standings (
  team_id int(3) unsigned NOT NULL AUTO_INCREMENT,
  points int(2) unsigned DEFAULT 0,
  goal_difference int(2) unsigned DEFAULT 0,
  goals_for int(2) unsigned DEFAULT 0,
  PRIMARY KEY (team_id)
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=latin1;

insert into standings(team_id,points,goal_difference,goals_for) values (1,20,2,17);
insert into standings(team_id,points,goal_difference,goals_for) values (2,14,8,15);
insert into standings(team_id,points,goal_difference,goals_for) values (3,9,2,11);
insert into standings(team_id,points,goal_difference,goals_for) values (4,14,10,12);
insert into standings(team_id,points,goal_difference,goals_for) values (5,17,10,19);
insert into standings(team_id,points,goal_difference,goals_for) values (6,5,-11,7);
insert into standings(team_id,points,goal_difference,goals_for) values (7,14,10,10);
insert into standings(team_id,points,goal_difference,goals_for) values (8,9,2,14);
insert into standings(team_id,points,goal_difference,goals_for) values (9,12,1,10);
insert into standings(team_id,points,goal_difference,goals_for) values (10,9,2,14);
commit;

我想按积分、goal_difference 和goals_for 的降序对该表进行排序，并根据此顺序为每个团队分配排名。由于 mysql 没有 RANK 功能，所以在搜索了这个站点后我来了 完成这个查询。

SELECT CASE
          WHEN @prev_value = concat(points,'-',goal_difference,'-',goals_for)
          THEN
             @cur_rank
          WHEN @prev_value := concat(points,'-',goal_difference,'-',goals_for)
          THEN
             @cur_rank := @cur_rank + 1
       END
          AS rank, s.team_id, s.points, s.goal_difference, s.goals_for
  FROM standings s, (SELECT @cur_rank := 0) p, (SELECT @prev_rank := 0) q, (SELECT     @prev_value := NULL) r
 ORDER BY s.points DESC, s.goal_difference DESC, s.goals_for DESC;

到目前为止一切顺利。现在我有两个问题。

如果您看到上述查询的结果，则第 8 队和第 10 队之间并列第 7 名。因此，我想将排名第 9 的团队分配给下一个排名第 3 的团队。我该如何做到这一点，而无需在查询中添加更多列。

我想使用此查询创建一个 VIEW。但是 mySQL 不允许我创建一个并给出错误，'View's SELECT contains a variable or parameter'。请建议如何为此创建 VIEW。

CREATE VIEW view_standings
AS
   SELECT CASE
     WHEN @prev_value = concat(points,'-',goal_difference,'-',goals_for)
     THEN
        @cur_rank
     WHEN @prev_value := concat(points,'-',goal_difference,'-',goals_for)
     THEN
        @cur_rank := @cur_rank + 1
  END
     AS rank,s.team_id,s.points,s.goal_difference,s.goals_for
FROM standings s,(SELECT @cur_rank := 0) p,(SELECT @prev_rank := 0) q,(SELECT @prev_value := NULL) r
ORDER BY s.points DESC, s.goal_difference DESC, s.goals_for DESC;

【参考方案1】：

您还可以使用相关子查询进行排名。如果您的数据量适中，这可能会产生大量计算。

 select s.*,
        (select 1+COUNT(*)
         from standings s2
         where s2.points > s.points or
               (s2.points = s.points and s2.goal_difference > s.goal_difference) or
               (s2.points = s.points and s2.goal_difference = s.goal_difference and s2.goals_for > sys.goals_for
        ) as ranking
 from standings s

因为它在from 子句中只有一个子查询，所以您可以将其用作视图。

我认为您可以通过索引号为standings(points, goal_difference, goals_for) 来提高性能。

【讨论】：

谢谢戈登。这正是我想要的。