添加外键约束时遇到问题（错误 ORA-02270：此列列表没有匹配的唯一键或主键）

Question

我正在学习如何使用主键和外键限制为 class 创建一个小而简单的数据库。 我在尝试运行我的 ALTER TABLE 语句时收到 ORA-02770，据我所知，这是通知我在外部表中引用的列未列为主键约束。 但是，据我所知，我的语法是正确命名 CREATE TABLES 语句中的主键的。 我在 all_cons_columns 表中搜索了 player_info 表，它也显示了列出的主键。 我能得到一些指导吗？ 下面列出的是我当前的脚本：

CREATE TABLE Player_Game
( school varchar2(30),
  player_number number(2,0),
  game_number number(1,0), 

  CONSTRAINT playergame_pk PRIMARY KEY (school, player_number,game_number)
);

CREATE TABLE School 
( school varchar2(30), 
  city varchar2(30), 
  coach varchar2(30), 
  team_name varchar2(30),
  win_record number (2,0), 
  loss_record number (2,0), 

  CONSTRAINT school_pk PRIMARY KEY (school)
);

CREATE TABLE Game 
( school varchar2(30),
  game_number number(1,0), 
  game_date DATE, 
  game_score varchar2(15), 

  CONSTRAINT game_pk PRIMARY KEY (school, game_number)
);

CREATE TABLE player_info
( school varchar2(30), 
  player_number number(2,0), 
  player_name varchar2(25), 

 CONSTRAINT playerinfo_pk PRIMARY KEY (school, player_number)
);

CREATE TABLE city 
( city varchar2(30),
  population number(5,0),

 CONSTRAINT city_pk PRIMARY KEY (city)
);

/*Here is the failing alter command */
ALTER TABLE Player_Game
ADD CONSTRAINT playergame_fk FOREIGN KEY (school) REFERENCES game(school); 

Answer 1

您在 alter table 语句的playergame_fk中有不正确的列列表。 外键的列列表必须与它所引用的主键的列列表完全匹配。

主键列列表是school, game_number ，因此，您的外键必须具有相同的列：

ALTER TABLE Player_Game
ADD CONSTRAINT playergame_fk FOREIGN KEY (school, game_number) 
  REFERENCES game(school, game_number);