Question

MySQL v5.0.58。

为了简洁起见，省略了具有外键约束等的表和其他不相关的细节：

CREATE TABLE `fixture` (
  `id` int(11) NOT NULL auto_increment,
  `competition_id` int(11) NOT NULL,
  `name` varchar(50) NOT NULL,
  `scheduled` datetime default NULL,
  `played` datetime default NULL,
  PRIMARY KEY  (`id`)
);

CREATE TABLE `result` (
  `id` int(11) NOT NULL auto_increment,
  `fixture_id` int(11) NOT NULL,
  `team_id` int(11) NOT NULL,
  `score` int(11) NOT NULL,
  `place` int(11) NOT NULL,
  PRIMARY KEY  (`id`)
);

CREATE TABLE `team` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
);

其中：

平局会将result。place设为0
result。place将包含一个表示第一名，第二名等的整数，等等

任务是返回一个字符串，描述给定团队在给定比赛中最近播放的结果。如果给定的团队胜利，格式应该是“def X队，Y队”，如果给定的队伍输了，则“输给X队”，如果有抽牌，则“与X队队员队员队伍”。是的，理论上每个灯具可能有两个以上的团队（尽管1 v 1将是最常见的情况）。

这很有效，但感觉非常低效：

SELECT CONCAT(
    (SELECT CASE `result`.`place` 
        WHEN 0 THEN "drew with"
        WHEN 1 THEN "def"
        ELSE "lost to"
        END
    FROM `result`
    WHERE `result`.`fixture_id` = 
        (SELECT `fixture`.`id` FROM `fixture`
        LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id`
        WHERE `fixture`.`competition_id` = 2
        AND `result`.`team_id` = 1
        ORDER BY `fixture`.`played` DESC
        LIMIT 1)
    AND `result`.`team_id` = 1),
    ' ',
    (SELECT GROUP_CONCAT(`team`.`name`)
    FROM `fixture`
    LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id`
    LEFT JOIN `team` ON `result`.`team_id` = `team`.`id`
    WHERE `fixture`.`id` = 
        (SELECT `fixture`.`id` FROM `fixture`
        LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id`
        WHERE `fixture`.`competition_id` = 2
        AND `result`.`team_id` = 1
        ORDER BY `fixture`.`played` DESC
        LIMIT 1)
    AND `team`.`id` != 1)
)

我是否错过了一些非常明显的内容，或者我是否应该在一次查询中尝试这样做？或者目前的难度是否反映了糟糕的桌面设计？

Answer 1

尝试选择您需要的数据（团队名称和目标团队的place），然后将其合并。对于每个夹具的两个团队：

SELECT CASE `recent`.`place` 
        WHEN 0 THEN CONCAT("drew with ", other_name)
        WHEN 1 THEN CONCAT("def ", other_name, ", ", targ_name)
        ELSE CONCAT("lost to ", other_name)
    END
FROM (SELECT rtarg.place, targ.name AS targ_name, other.name AS other_name
        FROM `fixture`
        JOIN `result` AS rtarg ON `rtarg`.`fixture_id` = `fixture`.`id`
        JOIN `team` AS targ ON `rtarg`.`team_id` = `targ`.`id`
        JOIN `result` AS rother ON `rother`.`fixture_id` = `fixture`.`id`
        JOIN `team` AS other ON `rother`.`team_id` = `other`.`id`
        WHERE `fixture`.`competition_id` = 2
          AND `rtarg`.`team_id` = @targ
          AND `rother`.`team_id` != @targ
        ORDER BY `fixture`.`played` DESC
        LIMIT 1) AS `recent`;

每个灯具可以通过最少的更改来处理两个以上的团队，但其他子查询也可以。

SELECT CASE `recent`.`place` 
        WHEN 0 THEN CONCAT("drew with ", other_names)
        WHEN 1 THEN CONCAT("def ", other_names, "; ", targ_name)
        ELSE CONCAT("lost to ", other_names)
    END
FROM (SELECT rtarg.place, targ.name AS targ_name, GROUP_CONCAT(other.name SEPARATOR ', ') AS other_names
        FROM `fixture`
        JOIN `result` AS rtarg ON `rtarg`.`fixture_id` = `fixture`.`id`
        JOIN `team` AS targ ON `rtarg`.`team_id` = `targ`.`id`
        JOIN `result` AS rother ON `rother`.`fixture_id` = `fixture`.`id`
        JOIN `team` AS other ON `rother`.`team_id` = `other`.`id`
        WHERE `fixture`.`competition_id` = 2
          AND `targ`.`id` = @targ
          AND `rother`.`team_id` != @targ
          AND ((rtarg.place<=1 AND rother.place >= rtarg.place)
            OR (rtarg.place>1 AND rother.place < rtarg.place))
        GROUP BY fixture.id
        ORDER BY `fixture`.`played` DESC
        LIMIT 1
) AS recent;

未指定每个灯具两个以上团队的结果格式，因此可能需要进一步调整。

当'WITH'不可用时避免重复的子查询

1 个答案: