标准化ID，其中行中存在2个FK

Question

我正在尝试创建一个标准化“运动装置”的视图，但是我在主题乐队表格中连续拥有主队和客队的ID。在尝试规范化这些时，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)

夹具有hometeamid和awayteamid团队有id和名字

我尝试了一个子查询，但它返回多个结果。

任何帮助/建议表示赞赏。

Teams Fixtures

Answer 1

你需要两次加入球队，一次是主队，一次是外出。

可以这样想：对于每个外键，你需要另一个连接。

虽然我不确定为什么你有多个连接到fixturef_testing一个用户和一个完成...

而且，我不喜欢把所有东西都放在后面。当我有一个reserved / keyword来使它更具可读性时，我宁愿只使用它。

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