Question

所以我需要加入5个表。其中一个我有问题。它有2列，它们是不同表的相同外键，即

matchdetail  
idmatch | idplayer1 | idplayer2 | time | (FK) idmatchnight (FK)

这是

之间的联结表

player
(PK) idplayer | firstname | secondname | nationality 

matchnight
(PK) idmatchnight | location

我的sql查询应该是什么？

我目前的代码：doent work

SELECT * FROM player
INNER JOIN coach ON player.idcoach = coach.idcoach
INNER JOIN sponsor ON player.idsponsor = sponsor.idsponsor
INNER JOIN matchdetail ON player.idplayer = matchdetail.idplayer1
                                        AND player.idplayer = matchdetail.idplayer2
INNER JOIN matchnight ON matchdetail.idmatch
WHERE player.idplayer=:idplayer
;"

idmatch是代理主键而不是复合键

Answer 1

重新编写查询可能会更好：

SELECT ...
FROM matchdetail
INNER JOIN player AS p1 ON matchdetail.player1=p1.idplayer
INNER JOIN player AS p2 on matchdetail.player2=p2.idplayer
etc...

您当前的加入基本上只允许玩家玩THEMSELVES的比赛。通过两次加入player，您可以获得两个不同玩家的详细信息。

Answer 2

如果您想保留此逻辑，您还可以使用OR代替AND：

SELECT * FROM player
INNER JOIN coach ON player.idcoach = coach.idcoach
INNER JOIN sponsor ON player.idsponsor = sponsor.idsponsor
INNER JOIN matchdetail ON (player.idplayer = matchdetail.idplayer1
                                        OR player.idplayer = matchdetail.idplayer2)
INNER JOIN matchnight ON matchdetail.idmatch
WHERE player.idplayer=:idplayer;

问题在于，使用当前谓词（使用AND），它基本上与以下内容相同：

player.idplayer = matchdetail.idplayer1 = matchdetail.idplayer2

Answer 3

SELECT columns, you, actually, want 
  FROM matchnight m
  JOIN matchdetail d
    ON d.idmatchnight = m.idmatchnight
  JOIN player p1
    ON p1.idplayer = d.idplayer1
  JOIN player p2
    ON p2.idplayer = c.idplayer2;

Answer 4

感谢大家的回答

我自己找到了一个解决方案：）

SELECT * FROM matchdetail
INNER JOIN boxer ON matchdetail.idplayer1
                    AND matchdetail.idplayer2
INNER JOIN coach ON player.idcoach = coach.idcoach
INNER JOIN sponsor ON player.idsponsor = sponsor.idsponsor
INNER JOIN matchnight ON matchdetail.idmatchnight = matchnight.idmatchnight
WHERE player.idplayer

PHP中的SQL查询，连接具有两列相同外键的表

4 个答案: