mysql - 关联表SQL语句

Question

我有 3 张桌子

Racer( racerID, racerName)
Race (raceID, raceName)
RaceJoinRacer(raceID, racersID)

我无法弄清楚将检索哪个“赛车手”参加了哪个“比赛”的 sql 语句。

这是我到目前为止所拥有的：

SELECT racerName, raceName 
FROM Racer, Race 
JOIN RaceJoinRacer 
    ON RaceJoinRacer.raceID= Race.raceID

Answer 1

您正在混合隐式和显式连接语法。不要在FROM子句中使用逗号。相反，使用两个JOIN语句，这INNER JOIN在 MySQL 中是隐含的。

SELECT
  racerName, 
  raceName 
FROM
  Race 
  JOIN RaceJoinRacer ON RaceJoinRacer.raceID = Race.raceID
  JOIN Racer ON RaceJoinRacer.racersID = Racer.racerID

如果您想包括Racer未参加任何比赛的表中的赛车手，请使用LEFT JOINbetweenRacer和RaceJoinRacer代替：

SELECT
  racerName, 
  raceName 
FROM
  Racer
  LEFT JOIN Racer ON RaceJoinRacer.racersID = Racer.racerID
  JOIN RaceJoinRacer ON RaceJoinRacer.raceID = Race.raceID

Answer 2

SELECT 
   racerName, 
   Race.raceName 
FROM Racer 
   JOIN RaceJoinRacer ON Racer.racerID = RaceJoinRacer.racersID 
   JOIN Race ON Race.RaceID = RaceJoinRacer.RaceID

Answer 3

SELECT r.racerName, c.raceName 
FROM Racer r
inner join RaceJoinRacer rj ON r.racerID = rj.racerID 
inner join race on c on rj.raceid = c.raceid