Question

我很抱歉这个头衔。只是我不知道如何解释这个问题，所以试着实现我的目标。

我有两张桌子：球员和球队。我怀疑是如何添加5个玩家，使用关系一对多就像一个团队为5个玩家，我试图更新团队中的玩家ID，但它只返回最后一个玩家ID。

create table if not exists player (
    p_id int auto_increment not null,
    p_name varchar(100) not null,
    p_number int not null,
    primary key (p_id)
);

create table if not exists team (
    t_id int not null auto_increment,
    t_name varchar(100) not null,
    t_player_id int null,
    primary key (t_id)
);

alter table team add constraint t_pk_player foreign key (t_player_id)
references player(p_id) on delete cascade;

stored prodecure创建player并返回id

DELIMITER $$
create procedure sp_create_player(in newName varchar(100), 
                                  in newNumber int, 
                                  out id_player int)
begin
    insert into player (p_name, p_number) values (newName, newNumber);
    -- get the id of player
    set id_player := last_insert_id();
end$$
DELIMITER ;

stored prodecure创建team并返回id

DELIMITER $$
create procedure sp_create_team(in newName varchar(100), out id_team int)
begin
    insert into team (t_name) values (newName);
    -- get the id of teams
    set id_team := last_insert_id();
end$$
DELIMITER ;

我怀疑他在stored prodecure到add player到team

DELIMITER $$
create procedure sp_add_player_in_team(in teamId int, in playerId int)
begin
    -- I tried to make set but it´s not work
    update team set t_player_id = playerId where t_id = teamId;
end$$
DELIMITER ;

测试stored procedure

-- 5 player
call sp_create_player('De Gea', 1, @id_player1);
call sp_create_player('Rojo', 2, @id_player2);
call sp_create_player('Pogba', 3, @id_player3);
call sp_create_player('Rashford', 4, @id_player4);
call sp_create_player('Ibrahimovic', 5, @id_player5);

-- 1 team
call sp_create_team('Manchester United', @id_team);

-- select all player and team
SELECT * FROM player;
SELECT * FROM team;

-- add 5 player to team
call sp_add_player_in_team(@id_team, @id_player1);
call sp_add_player_in_team(@id_team, @id_player2);
call sp_add_player_in_team(@id_team, @id_player3);
call sp_add_player_in_team(@id_team, @id_player4);
call sp_add_player_in_team(@id_team, @id_player5);

-- select all player in team
SELECT t_player_id FROM team WHERE t_id = @id_team;

有什么建议吗？

Answer 1

您可能会向后或过于简单地表达这种关系。如果玩家属于一个团队，并且只有一个团队，则玩家记录应该参考团队记录。

如果玩家可以在多个团队中，那么你将拥有多对多的关系;这需要一个额外的表格，将球员与他们所在的球队联系起来（并因此与球队的队员联系）。

您可能希望团队直接引用玩家的唯一情况是，如果您使用此类引用来指定团队＆＃34;队长＆＃34;或类似的东西，只有一个团队。如果您允许联合队长，或者想要在该团队中确定玩家的角色，那么它可能会更好地作为链接表上的列。

插入值来更新mysql中的外键

1 个答案: