更正多个外键的外键约束的语法

Question

根据此示例，对于多个外键的foreign key constraint，所有引用来自引用表的相同primary key的正确语法是什么？

ALTER TABLE team
ADD CONSTRAINT fk_team_players
FOREIGN KEY (player_1, player_2, player_3, player_4, player_5, player_6, player_7, player_8) 
REFERENCES player (player_id)

Answer 1

你必须分开进行：

ALTER TABLE team
ADD CONSTRAINT fk_team_players1
FOREIGN KEY (player_1) 
REFERENCES player (player_id)

ALTER TABLE team
ADD CONSTRAINT fk_team_players2
FOREIGN KEY (player_2) 
REFERENCES player (player_id)

...
ALTER TABLE team
ADD CONSTRAINT fk_team_players8
FOREIGN KEY (player_8) 
REFERENCES player (player_id)

您也可以按照以下一条指令进行操作

ALTER TABLE team
ADD CONSTRAINT fk_team_players1 FOREIGN KEY (player_1) REFERENCES player (player_id),
ADD CONSTRAINT fk_team_players2 FOREIGN KEY (player_2) REFERENCES player (player_id),
...  
ADD CONSTRAINT fk_team_players8 FOREIGN KEY (player_8) REFERENCES player (player_id),

我建议您更改表格结构，以使玩家不在列中但在行中的其他表格中。