Correct syntax for foreign key constraint for multiple foreign keys

Question

As per this example what is the correct syntax for a foreign key constraint for multiple foreign keys that all reference the same primary key from the referenced table?

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

You have to do them separately:

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)

you can also do it in one instruction as below

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),

I recommend you to change table structure to keep players not in columns but in other table in rows.