不能添加外键约束

Question

我不能一个外键约束添加到我创造它的错误了这样一个数据库，也请让我知道，如果有问题，我的逻辑设计，我想创建一个REST API利用这个数据库结构。我想练我的数据库设计技巧，所以这是一个玩具的例子。

当前数据库架构

use ToolsDB;
create table player(
   player_id INT NOT NULL AUTO_INCREMENT,
   firstname VARCHAR(100) NOT NULL,
   lastname VARCHAR(40) NOT NULL,
   nickname VARCHAR(40) NOT NULL,
   wins integer,
   losses integer,
   current_win_streak integer,
   created DATETIME,
   last_seen DATETIME,
   PRIMARY KEY ( player_id )
   );


create table Attacker_Battles(
    attacker_id INT NOT NULL AUTO_INCREMENT,
    battle_id INT NOT NULL,
    player_id INT NOT NULL,
    PRIMARY KEY ( attacker_id ),
    FOREIGN KEY (battle_id) REFERENCES Battles (battle_id),
    FOREIGN KEY (attacker_id) REFERENCES player (attacker_id)
    );
create table Defender_Battles(
    defender_id INT NOT NULL AUTO_INCREMENT,
    battle_id INT NOT NULL,
    player_id INT NOT NULL,
    PRIMARY KEY ( defender_id ),
    FOREIGN KEY (battle_id) REFERENCES Battles (battle_id),
    FOREIGN KEY (defender_id) REFERENCES player (defender_id)
    );
create table Winner_Battles(
    winner_id INT NOT NULL AUTO_INCREMENT,
    battle_id INT NOT NULL,
    player_id INT NOT NULL,
    PRIMARY KEY ( winner_id ),
    FOREIGN KEY (battle_id) REFERENCES Battles (battle_id),
    FOREIGN KEY (winner_id) REFERENCES player (player_id)
    );

create table Battles(
    battle_id INT NOT NULL AUTO_INCREMENT,
    starttime DATETIME,
    endtime DATETIME,
    PRIMARY KEY ( battle_id )
    );

10:32:30    create table Attacker_Battles(  attacker_id INT NOT NULL AUTO_INCREMENT,  battle_id INT NOT NULL,  player_id INT NOT NULL,     PRIMARY KEY ( attacker_id ),  FOREIGN KEY (battle_id) REFERENCES Battles (battle_id),     FOREIGN KEY (attacker_id) REFERENCES player (attacker_id)     )    Error Code: 1215. Cannot add foreign key constraint 0.020 sec

Answer 1

你不需要attacker_id作为attacker_battles表的外键，因为它是主键。我想你想的player_id链接到player表。所以使用player_id外键。