mysql - 规范化行中存在 2 个 FK 的 ID

Question

我正在尝试创建一个 View 来标准化“体育赛事”，但是我在赛程表中连续显示了主队和客队的 ID。当尝试标准化这些时，我如何获得相关团队的团队名称？

select cast(`f`.`datetime` as date) AS `date`
     , cast(`f`.`datetime` as time) AS `time`
     , (select `t`.`name` 
        from (`fixturef_testing`.`teams` `t` 
        join `fixturef_testing`.`fixtures` `f` 
          on((`f`.`hometeamid` = `t`.`id`))) 
        where (`t`.`id` = `f`.`hometeamid`)) AS `hometeam`
     , (select `t`.`name` 
        from (`fixturef_testing`.`teams` `t` 
        join `fixturef_testing`.`fixtures` `f` 
          on((`f`.`awayteamid` = `t`.`id`))) 
        where (`t`.`id` = `f`.`awayteamid`)) AS `awayteam`
     , `u`.`name` AS `referee`,`c`.`name` AS `competition` 
from ((`fixturef_testing`.`fixtures` `f` 
left join `fixturef_testing`.`users` `u` 
  on((`u`.`id` = `f`.`refereeid`))) 
left join `fixturef_testing`.`competition` `c` 
  on((`c`.`id` = `f`.`competitionid`))) 
where (`f`.`active` = 1)

赛程有主队和客队id团队有 ID 和名称

我尝试了子查询，但它返回多个结果。

感谢任何帮助/建议。

Teams Fixtures

Answer 1

您需要加入球队两次，一次为主队，一次为客队。

这样想:对于同一个表的每个外键，您需要另一个连接。

虽然我不确定为什么你有多个连接到fixturef_testing，一个用于用户，一个用于完成......

此外，我不喜欢将所有内容都放在后面的勾号中。我宁愿只在有保留/关键字时使用它以使其更具可读性。

SELECT cast(f.`datetime` as date) AS `date`
     , cast(f.`datetime` as time) AS `time`
     , HT.Name hometeam
     , AT.Name awayteam
     , u.name AS referee
     , c.name AS competition
FROM fixturef_testing.fixtures f
--Are the next 2 joins really needed?--
LEFT JOIN  fixturef_testing.users u 
  on u.id = f.refereeid
LEFT JOIN  fixturef_testing.competition c 
  on c.id = f.competitionid
--Not sure what the above joins are for...
--Get the table Teams record for the home team
LEFT JOIN Teams HT  
 on HT.ID = f.hometeamID 
--Get the table Teams record for the away team
LEFT JOIN Teams AT
 on AT.ID = f.awayTeamID
WHERE f.active = 1