Question

所以我想展示最有经验的玩家，起初我会显示所有玩家和经验值，然后尝试只显示最大值。所以继承了表和查询本身的代码

CREATE TABLE Player    
(    
  Player_ID INTEGER CONSTRAINT pk_player PRIMARY KEY,    
  Pname VARCHAR(60),  
  DOB    VARCHAR(10),    
  Heightcm NUMBER(10),    
  Weightkg NUMBER(10),    
  Position VARCHAR(20),    
  Team_ID INTEGER CONSTRAINT fk_player REFERENCES Team(Team_ID)
)

CREATE TABLE PlayerCareer_Performance   
(    
  Player_Performance_ID INTEGER CONSTRAINT pk_PP PRIMARY KEY,    
  Player_ID INTEGER,    
  total_points NUMBER(10),    
  total_fouls NUMBER(10),    
  ExperiencePoints NUMBER(10),    
  CONSTRAINT fk_Pp FOREIGN KEY (Player_ID) REFERENCES Player(Player_ID)
)

这是表格代码，下面是查询：

SELECT PLAYER.PLAYER_ID,PLAYER.PNAME,PLAYERCAREER_PERFORMANCE.EXPERIENCEPOINTS    
FROM PLAYER    
JOIN PLAYERCAREER_PERFOMANCE    
ON PLAYERPERFROMANCE.PLAYER_ID = PLAYER.PLAYER_ID;

播放器在黄色下划线，并显示“与连接图的其余部分断开连接”

任何想法，任何人？我看不出它的解决方法:(

Answer 1

乍一看，您正在加入表PLAYERCAREER_PERFORMANCE，但加入了一个名为PLAYERPERFROMANCE （原文如此）的表格字段。这是一个错字吗？

此：

SELECT Player.Player_ID, Player.Pname, PlayerCareer_Performance.ExperiencePoints
FROM Player
JOIN PlayerCareer_Performance 
ON PlayerCareer_Performance.Player_ID = Player.Player_ID

似乎工作正常（刚纠正错字）：check it at sqlfiddle。

作为一般建议，保持代码一致......您正在使用不同的列格式（例如：ExperiencePoints vs total_points），并将所有SQL查询代码放入大写字母中很难阅读和找到拼写错误

Answer 2

使用内部联接（更新以反映大众需求）：

select p.player_id, p.pname, pcp.experiencepoiuts
from Player p
inner join PlayerCareer_Performance pcp on pcp.player_id = p.player_id

SQL Join - 查询错误

2 个答案: